The party conventions begin

July 18, 2016 by Sam Wang

The Republican Party’s national convention starts today [schedule]. Conventions are a chance for a political party to showcase their unity, their candidate, and their policies. Next week the Democrats take the national stage. Viewers will get a fairly direct contrast.

As measured via state polls, the Presidential race shows Hillary Clinton slightly ahead of where Barack Obama was at this point in 2008 and 2012. So far, the 2016 race has been stable.
History of Popular Meta-Margin for Obama
National polls suggest that undecideds account for about 5 percentage points more of the electorate than the Obama-Romney race, and Trump is particularly weak in states won by Romney. Based on these numbers, Trump needs to bring Republican voters home.

Downticket, in many key Senate races, general-election candidates are not known yet. I will not have anything to say about that for a few weeks. For now, a more interesting indicator of downticket sentiment is the generic House preference, which is currently at Democrats +7.5%. If that were to hold up, Democrats would have a good shot at retaking control of the House. However, preferences can change. Based on past years, it should take at least a month for us to get a fuller picture of where the national House race is headed.


Olav Grinde says:

I too am especially interested in the possible prospects of a Democratic-controlled Congress.
Question: How many districts are there where a +7.5 % D vote might have flipped the result this November – but in which the Democrats are not fielding a candidate?
…what you have previously called political malpractice.

Jason Bandlow says:

Thanks for the update! FYI, I’m seeing the 2014 Congressional preference graph, both above and on the left sidebar.

Sam Wang says:

Odd, I see the regular graphs. Reload? I will look into it too.

Ilan says:

I’m seeing the same thing as Jason. Just the 2014 Congressional preference graph.

Karl Hudnut says:

This is really a reply to Sam. On an iPad I see the 2014. If I click on the graph, I get the 2016. On Mac O/S 10.x, the correct graph shows up. So it is a code forking problem, generically speaking. Good hunting.

sc says:

Likewise for me, it’s seemed to alternate between 2014 and 2016 views for House and Senate both (more often 2014). I assumed this was some glitch while transitioning an auto-update script or something.

Jason Bandlow says:

Strange… Looks fine now. Thanks.

A New Jersey Farmer says:

Sam, what would qualify as a convention bounce or bump? I’m sure the media will talk about it, but is there a statistical definition or threshold?

538 Refugee says:

I think we will see a party ‘unification bump’ on both sides. Trump has more upside potential to be sure. “Not Hillary” will watch him at a closely controlled convention and ‘decide’. “Not Trump” will do the same thing with the DNC. I wouldn’t be surprised if the real bump isn’t undecideds going down with a little tightening.

Matt McIrvin says:

The conventions are unusually early this year, which may make them less important in terms of affecting the November result. (Though convention bounces usually fade pretty rapidly.)

FearItself says:

This thought occurred to me yesterday: given that the public has a net negative view of him, is it conceivable that Trump’s convention “bounce” might actually be negative? What do you think?

Paul says:

Hey Sam, long time reader. I’m curious if you have any thoughts about why the Senate MM seems so dubious for the Dems right now. It’s tempting to say that voters are hedging against a Hillary victory by remaining more supportive of Republican incumbents, but I don’t know if there’s much to back that up. Any thoughts? Tx.

Sam Wang says:

Most nominees aren’t certain yet. Wait until August/September.

Josh says:

The dems have to pick up a lot of seats to gain the majority. The fact that they are highly likely to pick up at least five is not trivial (or “dubious”)… I do wonder if the Evan Bayh announcement has factored into polls yet though…

mediaglyphic says:

a little off topic but i wonder if the graph you posted on July 7th comparing current polls, with 2012 outcomes, would be more relevant if we compared, current polls with polls in July 2012?

Josh says:

Sorry for the off-topic question but I’ve been wondering: why is NH worth more “Jerseyvotes” than NV? If Clinton is +4 in NH but only +1 in NV, wouldn’t a vote be more relevant in NV?

Steven says:

Size of the electorate?

Matt McIrvin says:

NH is closer to the overall Meta-Margin for the whole country. If Clinton loses Nevada, she could still be ahead nationally by a few points and there are a lot of ways for her to still win. But if she’s losing New Hampshire, she’s probably very close to the edge between winning and losing, so the chance of it determining the election is greater.
Also, the “Jerseyvotes” are calculated for an individual voter, which I think actually gives a bonus to the smallest states because an individual voter is more likely to swing a small state–and because for a small state, the fraction of an electoral vote per individual person is larger.

Josh says:

Thanks Matt and Steven; makes sense that it’s related to size of the population (lower denominator= more value). Matt I’m not sure if your other point works for me– I think the Jerseyvotes only reflect the likelihood of changing the outcome in a state, not of winning the overall election… it seemingly has nothing to do with winning the overall election because today Ohio –generally considered a crucial state– is dead even in polling and yet the Jerseyvote value is wayyyy down at 30. So it must have a lot to do with the electorate size and only a little to do with how close the polling is in that state…?

Matt McIrvin says:

According to Sam’s FAQ, it’s definitely the effect on the national win probability being computed here. I think the point with Ohio is that, in this cycle, it’s actually not as crucial as the conventional wisdom would imply. Look at the map right now: Ohio (and Iowa) are on the brink right now, but the whole map is clearly not on the edge of a Trump win. If both of them flipped, Clinton would still be in the lead.
So the chance of them affecting the overall result, while higher than for most states, is not as high as for, say, Pennsylvania: by the current modeling, PA flips only when the whole result is very much in jeopardy.
And then on top of that, there’s the bonus for an individual voter’s effect on smaller states that raises the jerseyvote value for states like NV and NH.

Sam Wang says:


Josh says:

Huh. Yeah I’m simply not smart enough to grasp this. The bottom 7 states in the Jerseyvote list range from Clinton +7 to +11, which intuitively says “right, Clinton is leading by so much that your vote is relatively unimportant as you get to the bottom of the chart”– EXCEPT, Ohio is thrown in there at dead even. And Florida is Clinton +1 yet Jerseyvote 42.8. So Florida and Ohio are apparently irrelevant, but NH somehow holds the key to the election… not because NH is important but because NH is blue enough to not flip until she’s already losing… but small enough that your vote matters… Yeah I’m trying to get it but it eludes me. To my brain, if NH won’t flip unless she’s already losing, then by definition NH is less relevant…
But I do understand the “size of the electorate” part. So that’s good. 🙂
To my brain, the most relevant vote is the one in the state that is some combination of smallest electorate yet closest in polls– so you can flip a state. NH is in the eastern time zone, so there is no way a NH vote is determining the election anyway…

Matt McIrvin says:

The idea that a Democratic House is actually more likely than a Democratic Senate is interestingly contrary to all conventional wisdom this year.

Matt McIrvin says:

Nate Silver is being very horse-racey with a trollish headline: Clinton’s Lead Is As Safe As Kerry’s Was In 2004
I think he’s trying to atone for dismissing Trump during the primary campaign.

DaveM says:

It’s worth noting that although the chart Silver presents in that article is labeled “Polls become much more accurate after the conventions,” the pre-convention polls in both 2008 and 2012 were closer to Obama’s ultimate margins of victory.

Froggy says:

Is it worth doing some temporary adjustment to handle the recent change in Democratic candidates for the Indiana senate race? You have Young +8.0 over Baron Hill, but Hill dropped in favor of Evan Bayh. The first poll out shows Bayh up by 21% over Young.

Sam Wang says:

Must update that. FYI, assumptions on candidate identity are visible here:

Michael Hahn says:

Off topic: BUT, what happened to the Obama approval rating?? !! The graph suddenly inverted for the past 7 months or more!!!! Is there a recent glitch, or has there been a long-standing glitch? All the polls listed on the left show Obama with a positive rating!!!

Sam Wang says:

HuffPollster helpfully changed their data format without telling us. We have fixed it now.

Mark F. says:

I would be highly surprised if the Dems take back the House. I think they will pick up around 10 seats. And keep in mind that 40 Senators can effectively block all new legislation, so don’t expect Bernie Sanders like policies to come out of a Clinton Administration even with a Democratic Congress.

DaveM says:

40 Senators can effectively block all new legislation as long as the majority elects to continue playing by the current rules.

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