Princeton Election Consortium

A first draft of electoral history. Since 2004

The Comey effect

December 10th, 2016, 10:06pm by Sam Wang


September 18, 2017: Re-upping it again because of that claim over at The Monkey Cage to the contrary. Nothing new to add, except that it is always possible to cast doubt on a fairly obvious claim if you use a method that makes your error bars large.

May 9th, 2017: I am re-upping this because of the recent column by Nate Silver on this topic. He had previously addressed the topic of Comey, shortly after the election. I thought he did a good job, both then and now.

I don’t entirely see the need to revisit the topic, which I regard as settled. To me, the other critique in the news illustrates the inadequacy of smoothing methods to forensically extract rapid changes like the Comey effect.

A month after Trump’s upset victory, the aftermath is still sending shocks through the United States and the world. In addition to a hard rightward move on policy, Trump, Pence, and Company appear to be bent on uprooting many institutions. The risk to the American system of government and life has been noted by both liberals and conservatives.

Hillary Clinton’s narrow loss to Donald Trump was influenced by many causes in the home stretch: complacency driven by conventional wisdom and polls (and yes, poll aggregation), which led to the media assumption that she would win, which in turn was a likely driver of the tone of coverage. And of course there is so much to say about the candidates themselves.

In mid-October, I said I didn’t think Trump would clear 240 electoral votes, a statement I paid for later by eating a bug on CNN. My error seems to be accounted for by two events: (1) undecided Republican voters coming home, and (2) FBI Director Jim Comey’s letter to Congress about Clinton’s email.

From opinion data alone, it is possible to estimate when a change occurred. This can test between alternative explanations, which include not only the Comey letter (October 28th) but preceding events such as the announcement a hike in Affordable Care Act premiums (October 24th). However, it is not possible to see the shift using the averaging methods used by other aggregators. They tend to smear results out over time. For example, the Huffington Post does not allow a sudden shift to be seen.

I calculated a day-by-day margin using polling data from the Huffington Post. These polls were done on multiple days, which I converted to individual dates using the following procedure:

  1. Made a large table with one date per column (spreadsheet here);
  2. For each survey, entered the Clinton-Trump margin across all dates covered by the survey sample;
  3. Calculated the median Clinton-Trump margin by date;
  4. Shifted the time axis by 3 days, to correct for the fact that each survey also covered earlier and later dates.*

The above graph shows the result. After the Affordable Care Act premium hike announcement, opinion did not move for days, arguing against this as a main driver of the late swing in opinion. It could still be a factor, as is the case for many events. But such an effect would have to be gradual.

However, the big change does coincide well with the release of the Comey letter. Opinion swung toward Trump by 4 percentage points, and about half of this was a lasting change. This was larger than the victory margin in Michigan, Pennsylvania, Florida, and Wisconsin. Many factors went into this year’s Presidental race, but on the home stretch, Comey’s letter appears to have been a critical factor in the home stretch.

*Based on reader feedback and some correspondence with Marcy Wheeler, this post has been modified. The original version is here. The graph is the same, it’s just shifted by three days to avoid “time travel,” in which the effect appeared to show up before the cause. This is a bit of a kludge: a fixed-interval correction is not possible because each survey was done over a different time period. A better alternative would be to calculate medians using only the final sampling date. I’ll try that out later – traveling at a conference now.

Tags: 2016 Election

47 Comments so far ↓

  • Lorem

    Somewhat relatedly, since she cites this very analysis briefly, I read Hillary’s book and I thought it was pretty on point and her thoughts are solidly founded in data / align with my understanding of events. She focuses more on her strengths and somewhat skimps on coverage of some negative points, but that’s to be expected from anyone.

    • LondonYoung

      IMHO, Sam’s analysis is narrow and pointed: the revelation that Hillary’s confidential emails were in the Weiner’s lap alongside his sexting cost her two points. This is pretty solidly founded (and the Monkey Cage is just “un-mathematical”).

      But none of us believed that two points would matter.

  • gumnaam

    I think a revisit, even if brief, may be warranted to clarify exactly how Nate Cohn errs in his methods in his recent counterintuitive column on the topic in the NYT.

    • gumnaam

      Otherwise, it is left hanging out there that the NYT (even the liberal NYT) does not think that Comey biased the election. Your opinion is considered trustworthy on this topic by many NYT readers, including me.

  • Denny

    Whatever the actual quantitative effect of the Comey letter was–and I can’t see how it could have been so insignificant, relative to the small margin of victory of Trump in Pennsylvania, Wisconsin, and Michigan, the spectacle of FBI Director James Comey’s weaving in and out of the 2016 presidential election (like a moth in front of an light-bulb) in the last two weeks clearly riveted, nationally and locally, negative attention on Hillary Clinton. I don’t see how it can be minimized.

  • Dave

    The polling error in this election is very similar to the polling error in the 2014 elections and in the 2015 Kentucky gubernatorial election. An unmeasured Republican vote that no one saw coming but that showed up on election day. For example, Mark Warner nearly lost his seat in VA, winning by 0.8 percentage points, despite leading in the final RCP average by 9.7 points. Orman, the Independent candidate in KS, led by 0.8 points in the RCP average and Pat Roberts won by 10.8 points. McConnell led Lundergan Grimes by 7.2 in RCP and won by 15.5. Ernst led Braley by 2.3 in RCP and won by 8.5. In 2015 in KY, Conway led by 3.0 in RCP and Bevin won by 8.7. Comey didn’t send a letter in the waning days of any of those campaigns, yet the late shifts were similar to the late Trump shift.

    It seems plausible, at least, that there is an unmeasured white working class vote that’s not being reflected in polls but is showing up on election day. Given the 2014 and 2015 experiences, it seems that the Clinton campaign should have been particularly attuned to this possibility and made sure it locked down WI, MI, and PA.

    • Sam Wang

      I think your explanation of 2014 and 2016 polling errors does not work. The reasons were probably different.

      Polling error is worse in off-Presidential elections: see my 2014 analysis. In the last graph of that essay, the polling error is not correlated with partisan preference. In contrast, this year’s polling error was specifically in Trump-voting states (6 points) compared with Clinton-voting states (0.2 points). Different pattern, therefore different cause.

  • seeker

    Why does nobody mention that voter suppression after SCOTUS gutted the voting rights act might explain most of the loss?

    Suppression might explain why national polls were mostly correct; state ones not; the notable fall off of minority voters; razor thin margins in key states. . .

    One key mechanism is described here:
    http://www.rollingstone.com/politics/features/the-gops-stealth-war-against-voters-w435890

    Unfortunately, no mainstream attention has been given to this, despite some pre-election coverage.

    There might be reason to criticise the above, article. However the complete silence concerning the whole topic seems to ignore an important possible explanation.

    • Allen

      I agree that voter suppression was a major factor. With all the pre-polling, exit polling and post-polling, I would think it should be possible to quantify the impact of voter suppression efforts. We should be able to get some idea of:

      - How many people went to vote but left without voting because the lines were too long (had to get to a job or take care of children, etc.)
      - How many people didn’t go to vote because they believed or were told that the wait would be longer than they could afford
      - How many people were turned away from the polls because they didn’t have the proper ID
      - How many people didn’t go to vote because they didn’t think they had the proper ID
      - How many people went to vote but their names were missing from the voter rolls or they were told they had already voted or were given some other reason why they couldn’t vote. (Crosscheck is just one of the issues here).
      - How many people fell for dirty tricks like flyers that were circulated saying:
      If you have any back debts or owe child support, you’ll be arrested if you try to vote
      Deliberately inaccurate information on where to vote or when to vote (“Republicans vote Tuesday, Democrats vote Wednesday” – hope no one fell for this one!)
      Employers refusing to give time off to vote
      Intimidation due to an large police presence at polls, or the presence of threatening individuals

      All of these tactics were aimed at suppression of minority (i.e., Democratic) votes. We should be able to get some idea of whether this changed the outcome of the election.

  • RJ Willams

    Dear Intelligent Discussion being held by respectful, articulate people,
    You give me hope. Desperately needed at this time, I might add. Thank you.

  • Ravi Rajmane

    Thanks Sam for your thoughtful reasoning, data dives, and discussion. I reassured myself in the final 10 days by reading and rereading your posts and these comments as an echo chamber in my mind. However, I could never quell that sucker punch I felt when the Comey letter came out that Friday at 2pm.

    The “Blue Wall” has always been hyperbole to me. Several of the previous margins for the Democrats int the Upper Midwest have been razor thin. The impact of voter suppression measures since 2012 in WI, MI, and PA among minority votes might have been crucial to Trump’s narrow victories.

    Finally, a comment tonight on Chris Hayes Show struck me as critical to Trump’s victory. Trump’s rise could not have occurred without framing Obama’s presidency as total failure, as regulation run amok, government and judicial overreach, and multicultural globalism as the new “Leviathan (as per Mark Levin).” The series of midterm, state house, and gubernatorial “shelackings” by Republicans in the Upper Midwest were the first undertow of this riptide that snatched victory from Hilary. I am sorry to see her career as a public servant come to a close.

  • Brian Bowen

    Your opinion is entirely reasonable. Another (I would argue) reasonable explanation is that the race, in the end. reverted to where it had been much of the race with a 4 pct or so Clinton lead (by the polls). Would we have ended up there without the Comey incident? We will never know.

    • Chichi

      The article claims, with data, that we would not have ended up there without the Comey incident. To rebuff the claim, you have to find issue with either the data, data collection or analysis method.

      Yours is just an opinion and not an explanation.

  • Marc

    I concur with Carter Griffin. We should look at state-level polls here to see if the effect is preset in WI, OH, PA, MI, FL, etc. Perhaps Google Correlate would be informative? Could it be used to extrapolate backwards from election day on a state-by state basis? How far back might such an extrapolation be valid? If it works, it might provide much more comparable results among the states.

  • Joseph Brenner

    From looking at the national trend-lines at realclearpolitics, I had the sense that what was going on is the Johnson supporters were gradually shifting over to Trump, and that was a big factor in reducing Hillary’s national lead to 2 points. (The Green supporters were already down at only 2 points, and didn’t budge much over that time period.)

    It is true though that the real “upset” here was focused in around four states, and the national numbers are at best a rough proxy for what was really happening there.

    Myself, I like the theory that everyone was convinced that Hillary would win, so they all felt they could safely vote for Trump as a protest.

  • TJ

    I met a lot of undecided Dem voters knocking on doors in PA the last few weeks. They seemed hungry for one more round of bad news on either candidate. I heard variations of “They seem equally bad to me,” many times. I also thinking his forced twitter silence was a simultaneous plus. Was there coordination with all this? I want to hope not but the timing seems interesting. And thank you Sam. I pumped up a lot of folks watching your math and have apologized to many who I told she was going to win.

    • Chichi

      I admire such data driven approach to reality. You should not apologize because of events that are beyond your control.

      That letter changed the everything about the race. Just before the letter, there was talk about Trump TV and Trump brand collapse, right after the letter, the talk was back about the election.

  • Carter Griffin

    And as one last attempt at being a pain in the neck. The argument you make is based off of an analysis of margin between Clinton and Trump nationally. The issue is of course that Clinton did win the popular vote, as the graph above would predict. The problem wasn’t Clinton’s margin nationally, but in a handful of Midwestern states. Is there enough data to do a similar workup in MI, WI, and PA? That’d be more interesting simply because those were the decisive states, and when shifts occurred and how they developed would be more informative to the actual election than a look at the national popular vote margin.

  • Carter Griffin

    Rudeness? Hell, come by where I’m at in four years, and I’ll buy you at least a drink or two. We’re nice, but I also am a fan of cutting to the point. First off, thank you for taking the time to respond and clarify your point. My appreciation means very little in the scheme of things, but for what’s it’s worth I do appreciate your response.

    I still would argue that the ACA premium increase is still likely to have had a non-negligible effect on the election. First off, Trump’s data people said that they were seeing a swing towards Trump before the Comey letter came out (https://www.bloomberg.com/news/articles/2016-11-10/trump-s-data-team-saw-a-different-america-and-they-were-right). And while they did say that after the letter that swing accelerated, that such a swing started before the letter came out leads me to believe that the letter was at worst one factor in Clinton’s loss, and not necessarily the key one. Simply put, I don’t really see the Comey letter affecting the decision of a black man in Wayne County, MI whether to vote or not, or most anyone who isn’t plugged in 24/7 to cable news or the political parts of the internet.

    Second off, as a partisan Democrat in IA, I’m less than willing to buy the idea that if not for Comey the Democrats win for the simple reason of how the rest of the ballot looked across the country. As has been the case for the past eight years, Democrats yet again got their asses kicked all across the ballot. As but one example, IA Democrats lost five seats in the state senate, making IA one of the the 25 states in the country with one party Republican government. And with all of that, I’m not sure I don’t disagree with those Republicans I’ve heard who have said that this was a Republican wave election where, if anything, Donald Trump may have under-performed compared to other Republicans across the country. While these things of course are cyclical and in the long term Democrats will return to power in many areas and parts of the government, falling for a comforting story about how if it wasn’t for Comey, Putin, and all sorts of meddling kids we would have won is far from helpful. It puts off actually dealing with what is going on to the Democratic party across the country, and addressing these issues sometime before Trump’s second inauguration.

    Also, while there were admittedly many problems with the USC tracking poll (like showing Trump with a higher percentage of the vote than Clinton by the end of the election), like Trump’s people it did pick up on a shift for Trump starting around the 24th of October. Again, prior to the Comey letter being sent to Congress. I will admit that just by eyeballing it, it looks like the Comey letter corresponds to an acceleration in Trump gaining support and Clinton losing support in the USC poll, Trump still started pulling away in the poll before the Comey letter.

    One last question for you, I know this is probably a dumb question but have written anything about how you deal with modeling turnout and how you account for undecided voters? In the Midwest, the reason why Clinton lost was that Democratic turnout collapsed compared to Obama 2012, in most states in the Midwest (IA, WI, MI, and OH if I remember correctly) that Trump won 2012 Obama would have won. Additionally, there were a significant number of undecided voters up until the very end (in MI, the Fri. before the election the Detroit Free Press put out a poll with Clinton having a 3-4 point lead, but as many undecideds as a percentage as Obama’s margin of victory in the state in 08). These two factors seem to me to be the most important in explaining why the polls in the Midwestern states didn’t foresee Trump winning those states, but knowing how your modeling is based purely on polling I don’t know whether these we addressed in any way.

    Anyways, thank you for responding to my comment and have a good rest of the day.

    • Kim Jorgensen Gane

      I’m a Michigan voter. I think Michigan was hit hard by the weakening of the Voting Rights Act which targeted minorities (and which our legislature is attempting to further weaken). I believe that impacted voter turnout here big time (in Benton Harbor, a predominantly African American community near me, previous polling locations were closed and at least one was moved at the last moment). I’m curious to know whether any of that could be tracked as well.

    • Mitch Golden

      While we’re being polite, perhaps we can include something a little more substantive than some Trump pollsters gloating after the election that they were right all along. Can you point to an analysis of the public polls that pointed that way?

    • Sam Wang

      ACA: It is possible that events such as the ACA premium hike would have an effect on opinion. However, if it did happen, it would have been gradual, on the grounds that it doesn’t appear in the data.

      Several factors get in the way of telling whether a news event has an effect. One is news penetration: it would have taken time for the ACA news to reach those who were affected. In addition, the number of such people was not that great. It could be that the news was bigger in right-leaning media, though that’s an audience that was already persuaded. It’s kind of like the Access Hollywood tape, which only reinforced Democrats’ views of Trump without moving opinion at all, which I suggested would be the case in my “Why Trump Stays Afloat” NYT piece.

      Another factor is the fact that some events take longer to make an impact. For example, the Clinton email story was a long drip-drip throughout the campaign. It was part of the story – but except for the Comey letter, there wasn’t a single-day email-related event that was sudden enough to be measurable. My own view is that the email story was a manufactured scandal without basis in fact, like the Swift Boat Veterans for Truth campaign in 2004 or the Obama birth-certificate story in 2008. It’s something new every four years.

      Finally, note that the Comey letter influenced as few as 4% of undecided voters (from undecided to Trump), or 2% of decided voters (from Clinton to Trump). With such polarized voters, it doesn’t have to be many people.

      USC/Dornsife: could be, but that poll is smoothed over time, which is exactly the problem I was trying to overcome here. It would be nice to know when that sample started including October 28th respondents, so we could tell whether the change truly started earlier.

      Undecided voters: Yes, I should calculate that over time too. As hinted at in my statement above, the Comey effect could come from undecided voters who suddenly found their voice. Seems likely, but it needs testing.

      Midwest turnout collapse: I have to think whether the data support that view. The problem is that there were a ton of Johnson and Stein voters compared with 2012 (they were both on the ballot then too).

      In all of the above points, a general theme is that the election results were the sum of many small factors. All of these add up. In approximately descending order of importance, the factors seem to include: polarization of sub-demographics, including white rurals and noncollege voters; Trump racism and unusual appeal/repulsiveness; Clinton negative press generally, including the email story; the Comey letter; voter ID/voter suppression; and where HRC chose to focus ground game and ads. It doesn’t seem possible to lay the Trump win on any one of these. One could attempt to quantify the percentage associated with each of these factors. But at this point, it seems more important to look forward, not backward.

    • Carter Griffin

      First off, if the NYT exit poll is to be believed, when sorted by when people claimed they chose who they were going to vote for, Clinton only won among those who decided prior to Sept. If I’m right on how I’m reading the way it displays information, the big thing wasn’t voters swinging for Trump when Oct. rolled around, but either choosing third parties or, more likely, simply not voting for President. But the point overall, I would think, is that during the general election Clinton struggled to convince people to vote for her, so while there may have been a magnification of that due to Comey’s letter, ACA premium spikes, whatever, it was still a trend that was ongoing. And given everything that has been coming out about the utter mismanagement of the Clinton campaign, I would argue that the most that could be said is one thing or another was the straw that broke the camel’s back, but that by that point the camel was pretty close to its factor of safety anyways.

      Furthermore, as an aside, unless you start going to the absurd lengths of saying that every Johnson and Stein voter would have voted for Clinton in a head to head match up, third parties really didn’t matter too much for Clinton. The only way that you get Clinton winning with third party voters is if, overall, you believe that every Stein and every Johnson voter would go to Clinton. Otherwise, with more realistic numbers, such as what an NBC (I think) exit poll had with 25% of Stein and Johnson voters going for Clinton, 15% of Johnson and 10% of Stein for Trump, and the rest staying home, Clinton wins MI but Trump still wins in WI and PA. On the other hand, a candidate who could point to third party votes affecting their performance is Donald Trump. Evan McMullin for example got over 100,000 votes in UT and in MN had a vote total about 84% of the margin between Clinton and Trump. Given that his entire raison d’etre was to give disaffected Republicans someone who they could stomach, if we’re positing realistic scenarios without third parties, we have to also consider that that could mean Trump does better, such as saying picking up MN, not worse.

      Finally, yes we do need to look forward. But we can’t look forward effectively if we don’t grapple with the problems that already exist within the Democratic Party. While I think it is fair to say at this point that Hillary Clinton was simply the wrong candidate at the wrong time, someone who for whatever reason insisted on running a campaign of a 2004 or 1996 vintage in 2016 among other problems, that still doesn’t deal with the issues afflicting the Party all across the ticket. These are issues that have existed for most of Obama’s two terms, and which create a positive feedback loop which strengthens the Republican Party in the states and at the national level. When people talk about voter ID laws and similar measures, it’s worth keeping in mind that the reason why those measures were implemented was due to the Republicans gaining sufficient control of state governments to implement them. If Democrats either controlled those state governments outright or had enough power to block Republican legislation, those measures wouldn’t be in place. To point to them as a cause, instead of as a symptom of greater issues facing the Democratic Party, is to miss the point entirely. Ultimately, we can’t move forward unless we have some idea of why we’re at where we are. If we continue on as we have been for the past several years now and truly believe that nothing must change, we likely loose in 2018, 2020, and however long it takes for the Democratic Party to reform in such a manner as to be able to win elections at all levels of government.

  • LondonYoung

    There is something else that happened at the same time as the Comey letter. The FBI leaked that the new emails found were on Anthony Weiner’s laptop. There are a lot of low information voters that don’t know what an email server is, but do know who Anthony Weiner is.

    I wonder what would have happened if Comey had not sent a letter, but the FBI had still leaked that HC’s emails were found on Weiner’s laptop.

    IMHO, “new emails found” didn’t swing any votes, but the leak “HC emails on Weiner laptop” did.

    • LondonYoung

      American history will look very different depending on whether Comey was reacting to a leaking Weiner, or was orchestrating it. The letter is very tame if he was merely responding to the leak. Had he not written it, and the leak happened anyway, the mess would have been far worse – Weiner is tabloid bait of the first magnitude.

    • 538 Refugee

      The excuse that he had to do it because it would have leaked otherwise is an absolutely unacceptable answer for the a person in Comey’s position. It shows his total lack of control over the agency. If that was his concern he should have made it clear that anyone found leaking that information so close to the election would face the severest penalties available to impose.

    • LondonYoung

      My point was that I think the Weiner leak may have preceded the letter.

      If you consider such a leak proof that Comey has total lack of control over the agency, take a look at the NY Times on any given day and count how many articles reference anonymous sources not authorized to speak for their department/agency/company/etc ….

      I have zero desire to defend Comey, but leaks are routine everywhere – on a typical day you will find a NY Times front page article that reference an anonymous source not authorized to speak.

    • 538 Refugee

      If the FBI can’t prevent leaks its whole mission is compromised. Comey was sure quick to condemn Clinton’s use of a private email server as reckless yet it appears his entire department can’t be trusted with classified material because it will be leaked anyhow? If they can’t investigate and determine who leaked then they seriously need some personnel changes. May as well start at the top.

    • LondonYoung

      Well, at the top is Obama, but he is already going. Then comes Loretta Lynch, Comey’s direct boss, but she is going too. Seems to me that Comey should resign once the new AG is sworn in.

  • Dave C.

    Can you extend the graph to show the effect of Clinton’s “deplorables speech”? In my personal discussions, that had a greater influence on opinions than did the Comey letter.

  • pechmerle

    While this discussion is analytically neat, it is overly-sophisticated for “what happened here.”

    shma reverts back to the crucial data, which are related to the fundamental problem with our presidential election system. That problem, of course, is that a tiny error in campaign effort (apparently, failure to get out about 100,000 aggregate more African-American voters in Philadelphia, Detroit, and Milwaukee) reversed the direction of outcome of the election, despite HRC winning approx. 2,000,000 more votes nationally than DJT (a 2,000 to 1 disproportionate effect?). This of course is only possible because of our “model-1787″ electoral college. This is the second time in five cycles we have had this non-congruent outcome.

    It is time to move on from autopsying 2016, and look toward what can be done before 2020. For myself, I’m looking to such efforts as the National Popular Vote act (my state has adopted it), support for organizations that actively litigate voting rights cases (e.g. the Brennan Center for Justice at NYU Law School), and efforts to combat gerrymandering of House and state legislature districting (the federal court win in Wisconsin on this is heartening, though will be subject to appeal) (Sam has been active on the gerrymandering issue).

    During the election campaign, Sam urged not just analysis but that effort be devoted to the closest Senate races. Now, effort must be devoted to those things that can be done despite R control of the three primary branches of the federal government.

    • Emigre

      I am surprised you did not include this possibility:
      https://medium.com/@lessig/the-equal-protection-argument-against-winner-take-all-in-the-electoral-college-b09e8a49d777#.est4hkzcx
      Was it because you discovered that the 14th would not work?
      “I need to go back for a closer look at how the 14th Amendment played in Bush v. Gore before commenting on this idea.”

    • pechmerle

      Emigre, I haven’t concluded that the 14th Amendment equal protection argument against the electoral college won’t work. But it’s an extremely complex legal question, one that deserves to be tackled. But it will take many weeks, not a few days. The relevant case law stretches back over a hundred years, with increasing frequency and intensity after Baker v. Carr (1962). There are also articles and blogs beginning to appear from law professors and others whose analytical take deserves to be taken into account.
      So I do intend to come back with a more considered view on this topic. Just don’t expect it any time soon. I want to avoid mere punditry on this significant question.

    • pechmerle

      P.S. As I did already say in the earlier thread, I don’t think (despite what Lessig and a few others are now urging) that this 14th Amendment challenge can work with respect to the 2016 election. The rules were in place and entirely known, and the E.C. winner not being the popular vote winner is not a new anomaly. It has occurred (counting this time) five times since 1787. Thus, I believe, to challenge application of the standardly-understood practices to the 2016 result, a voter would have had to begin such a challenge a couple of years ago. (Or perhaps a challenge by a disadvantaged state such as Cal. or N.Y. as a few are suggesting, though I think a challenge by a voter would actually be stronger.)

    • Emigre

      I’ll be patient pechmerle!
      As you typed, the emphasis now should be on 2020 and how to bury the EC before then. I have no background in legal matters but am inclined to expect a law suit to be more promising than waiting (and waiting, and …) for more states to sign on to the National Popular Vote act.

  • Tom Hail

    It seems to me that Clinton and Trump wouldn’t have been close enough for the Comey letter to matter if it hadn’t been the constant “Crooked Hillary” and “Lock Her Up” mantra fueled by the Russian fed Wikileaks bullshit. Wikileaks dragged her down, Comey pinned it.

  • Carter Griffin

    I may not be an Ivy educated type, but I still think I can see bullshit when I see it. According to this chart Clinton’s lead started collapsing around the 23rd of October, but Comey’s letter was sent on the 28th. So did the “Comey effect” have some sort of sci-fi psychic effect on the electorate, such as to render traditional notions of causality meaningless? Or, since the news came out that premiums under the Affordable Care Act would go up significantly came out on the 24th, is it more likely that the drop in Clinton’s margin over Trump was more an effect of that news. At least that would have a cause and effect relationship that wouldn’t need Treknobabble to explain. Credit where credit is due by the way:(https://www.emptywheel.net/2016/12/11/obamacare-not-comey-effect/)

    • Sam Wang

      Despite your rudeness (I thought people from Iowa were supposed to be nice!) you have made a reasonable point.

      I agree there is some ambiguity of the type you describe. I’ve now explained it better in the post. Basically, on any given day, a poll that is in the field will usually also sample days before it and after it. An event on October 28th affects data points that are labeled as early as “October 25.” Therefore the axis is indeed a bit hard to understand – but still consistent with the explanation I offer.

  • 538 Refugee

    While Comey was the source, Trump and allies got away with making much more of it than it was and went largely unchallenged by themainstream press. In fact, I’d say aided by the press. “Lock her up.” “Pending indictment.” “Constitutional crisis.” While trying to portray neutrality the mainstream press allowed out right lies to go unchallenged. The networks might decry ‘fake news’ but their coverage helped spread it without debunking.

  • Alan Cobo-Lewis

    Sam,
    In 2004, when the polls were pointing toward a W re-election, you put in an assumption that undecideds would break toward Kerry. That assumption was unfounded, which is why the prediction failed (even though the underlying model’s prediction was spot-on). You learned your lesson. So this year, when undecideds broke toward Trump, I thought “what the heck–this is new”. And now we appear to know why.

  • Jan Oxenberg

    Did Comey’s action violate the Hatch Act? It’s a threat to our democracy that an intervention from the FBI clearly in collusion with Trump campaign (Giuliani boasted that something big was coming from FBI) not only could have – but likely did – change the result of the election. What is to be done? Where is the Justice Department?

  • shma

    While it’s a good exercise to ask what caused the polls to be off, I think it’s best to examine your model assumptions and see where improvements can be made. I can think of several methodology choices for the PEC model which contributed to the prediction error:

    First, it’s clear that the size of final polling errors are not predicted by the national poll (or meta-margin) volatility in the lead-up to election day. This was indeed a very stable election with regard to national poll volatility. But using that volatility, or a fixed number based on volatility from previous elections, as the standard deviation of the meta-margin distribution does not yield a good estimate of the distribution of final outcomes.

    Second, as Silver has mentioned, the percentage of 3rd party voters and undecideds near election day is correlated with final state poll error, and that should be reflected in the model as an extra systematic error for polls.

    Third, using a single national number like the meta-margin to encode the correlation in pollster errors across states ignores important information that you can only get from looking at a state-by-state correlation matrix. As you mentioned in your NYT piece, pollster error in states Trump won were significantly different than in states Clinton won. Rust-belt states (including Minnesota) all moved towards Trump by similar margins, while Florida and NC moved only slightly right.

    Finally, and this is true of almost all aggregators, a re-think of the “polls-only” approach is needed. Most aggregators, even if they use demographic or economic information in their models, tend to rely almost exclusively on poll results by election day. A model which incorporates significant demographic/economic parameters through election day may have done a better job at predicting the results.

    Whether you agree with any of this or not, it’s clear a full review of methodology is in order. It’s not just a Garbage In Garbage Out poll problem.

  • Jay Sheckley

    Not sure if this is the same topic, but now that the CIA says it happened,
    How can we quantify the effect of Russian hackers?

  • bks

    The Comey letter plus HRC fainting in public on 9/11 were the deciding factors (IMO).

  • Bulgakovs Cat

    Comey is a symptom– the cause is brain science and identity politics.
    Red brains arent bright enough to see the con, and the media is just a cash machine now.
    The GOP leadership is bright enough to see the con, but plans to leverage it anyways.
    The GOP leadership and the media have failed in their jobs.
    tant pis.

    • Johnny Monroe

      You know I have been reading this drivel long enough. I wanted to understand the reasoning behind the failure of the far left to accept the results of this past election. But as a highly successful, self-educated former liberal, and my education does not only include the writings of the liberal based world, I find your denigration of an entire sector of this country, ‘Red brains” more Xenophobic than nearly any writing short of Hitler, I would dare you to put your secular leanings to the test and look to your own family and those around them and see how many of these ‘red brains are among those you may know and then speak to me of their lack of a thought process.

      I would put my education, both formal and informal up to yours in a moment and know that at every turn I would be a step ahead of you. I do not pander my ideas or ideals to only those of like thinking, what a waste of your time and intelligence, but I freely share my views with anyone who cares to listen and make clear, valid rebuttals to my thoughts. I am intelligent enough to then modify my held beliefs to accommodate a shift in my thinking. Somehow I don’t believe you have the same ability.

      Yes, I left home at 17 and managed to support myself and my family, but I had enough respect for my family, my friends. and elders to know that everyone is entitled to their opinion, it is not right or wrong it is simply not mine. I do not, nor will I ever surround myself with only those of like minds, again I find this xenophobic, but it enriches my life and my mind and gives me a tolerance for their opinions, they are valid.

      I think you should grow up and expand your horizons, quit looking at the world through the mindset of a twelve year old, and accept what has happened in the vote. There is a valid reason for the electoral college, I would not care for the opinions of those in a few highly populated states determining my future based upon their high preponderance of ‘other minded’ thinking. Come to the realization that despite our being one country we are all secular in some respects, we all want our voices heard and represented. We do not want our opinions and needs dictated by those on either coast of the great country.

      Despite your thoughts we do all value where we live and our individual lifestyles that are, yes, somewhat determined by where we live and how we think. I have had the fortune and opportunity to live in many parts of this country and, yes traveled to and visited other parts of this world. As Americans we are truly gifted to be born here, our options and opportunities are virtually endless and incomprehensible. Many parts of the world envy us, many hate us for these same reasons, but we as Americans take so much of this for granted, it is our birthright, and give no thought to the poverty and lifestyles of any other parts of the world. These are the peoples you should be working to help with your high ideals, give them more opportunity, show them the how we as a country would bring to them a richer life, look to the reservations of Native Americans and see the abject poverty and lack of hope that abounds there as in the ghettos of this country. Reach out yourselves and help these people, get out of your comfort zone and do something that makes a difference in lives, don’t just give your ideals lip service.

      I think if you were to visit where we have left our countries original occupants you, as myself find tears in your eyes but it gives me an understanding and heartfelt belief in Henry Ford’s quote “Any man who thinks he can be happy and prosperous by letting the government take care of him better take a closer look at the American Indian.” Let your life make the difference in another’s, not in words and thoughts but in deeds. Find a way to change this world for the better. Words have never put food on a plate.

  • Ed Brown

    I am wondering if Clinton minus Trump polling margin is a useful quantity for predicting results? If there are approximately zero undecided voters, clearly it is a useful quantity with predictive power. If the percentage of undecided voters is equal to the C minus T polling margin, is the C minus T polling margin less predictive? What if the percentage of undecided voters is 2, or 3, or 4 times the C minus T polling margin? 10 times? At some point we lose predictive power. I am just wondering about this and hoping to learn a bit from reading responses from others.

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