Princeton Election Consortium

A first draft of electoral history. Since 2004

Partisan Gerrymandering Across the 50 States

July 16th, 2017, 8:49am by Sam Wang

Note: I’ll pretty this up later. In the meantime, the files are available for you to download and inspect at the end of this post.

Over at the Associated Press, reporter David Lieb has published a new, in-depth analysis of the effects of gerrymandering in the 2016 Congressional and statehouse elections. The analysis found that the same states identified as partisan gerrymanders in 2012 and 2014 in my Stanford Law Review article — North Carolina, Michigan, Pennsylvania, and Maryland — also show clear signs of advantage to the same political paty.

The analysis is important for two reasons: (1) It means that the advantages built into the district maps in 2012 aren’t dissipating, and that these gerrymanders will likely hold up through the 2020 elections, and (2) These advantages aren’t an accident, because they are echoed at the level of state legislatures. In short, the parties that were in power in 2011 are likely to have a strong hand in drawing the maps again in 2021. They will go unfettered unless the opposing party gains the governorship*.

While the AP report primarily relies on the “efficiency gap” analysis, the Princeton Gerrymandering Project provided a separate t-test** analysis of election results for the article. The agreement between the two tests is striking. Virtually*** every state flagged by the t-test at the Congressional level is also flagged by the efficiency gap. Generally, we have found that the efficiency gap does well except for having a higher false-positive rate than the t-test, which is unsurprising since the t-test has such a venerable history. At the state legislative level, 4 of the 6 worst offenders according to the efficiency gap are also captured by the t-test with exceedingly low p-values.

The results of our analysis of Congressional races can be found here, and results for state house elections can be found here.

I thank Brian Remlinger and Naomi Lake for assistance with this post.


*Currently, the opposition party holds the governor’s mansion in Pennsylvania (Tom Wolf, a Democrat) and Maryland (Larry Hogan, a Republican). Note that in North Carolina, the governor has no role in redistricting.

**A note on statistical testing: Our analysis used one- or two-tailed t-tests, depending on redistricting authority. For states with single party control of redistricting, we carried out one-tailed tests for advantage in the direction of that party. For states with bipartisan or nonpartisan redistricting, we carried out two-tailed tests.

***The exception is California, whose top-two primary system complicates analysis.

→ 2 CommentsTags: 2012 Election · 2014 Election · 2016 Election · governors · Redistricting

Benjamin Wittes on Politics & Polls

July 13th, 2017, 4:52pm by Sam Wang

Benjamin Wittes of Lawfare joined Julian Zelizer and me today on Politics & Polls. He gave us an unsparing look at potential crimes & what the Trump-Russia scandal looks like to the national-security community. Listen:

→ 1 CommentTags: President · Princeton · U.S. Institutions

Sharp cutbacks at HuffPost Pollster

June 15th, 2017, 2:21pm by Sam Wang

This is terrible news. As part of cutbacks at the Huffington Post, the tracking of polls will be curtailed dramatically. As reported by HuffPollster’s Ariel Edwards-Levy, they will only be tracking Trump’s favorability/unfavorability. All the other charts are now frozen. Evidently that includes the
generic House ballot, which I think is quite important.

This is a tremendous loss. The Princeton Election Consortium relies on their feed. They curate data, they apply their judgment, and they generate a structured API for dozens of races every year. It’s been a wonderful resource.

Personally, I would be willing to pay for such a feed. However, I’ve never been asked. Also, it’s not obvious whether there are enough subscribers to sustain their work.

I hope they re-expand operations in the future. In the meantime, I thank the many people who make HuffPost Pollster possible: Ariel Edwards-Levy, Janie Velencia, and before that Natalie Jackson, and before that Mark Blumenthal, and too many others to list here.

Here’s one of my favorite charts of theirs: the generic Congressional ballot. It’s for aficionados…but I do love it.

→ 7 CommentsTags: Politics

R.I.P., Adam West

June 10th, 2017, 11:54am by Sam Wang

My favorite version of Batman.

→ 1 CommentTags: Uncategorized

Overcoming your own brain’s bias in the Comey/Trump case

June 7th, 2017, 6:21pm by Sam Wang

Our brains have powerful biases that help us maintain a coherent world view. However, sometimes those biases prevent us from integrating new evidence well. Today, the release of former FBI director James Comey provides an example. Most readers on the left and the right see it as powerful evidence that President Trump attempted to obstruct justice, or at a minimum, tried to influence Comey improperly. But some defenders of Trump do not see it that way.

A powerful trick for overcoming biases is to “consider the opposite“: imagine that the story was the same, but reversed in some crucial way. That can lead evidence to look quite different.

In this case, here is how it works. Suppose that you are a Republican voter. Therefore your sympathies might naturally lie with Trump. In that case, imagine that Comey’s statement concerns not Donald Trump, but Barack Obama. In that case, it reads like this:

Ponder that as you work out your response to the evidence.

→ 14 CommentsTags: Politics · President

Politics & Polls: Teen Vogue’s Lauren Duca

June 1st, 2017, 3:20pm by Sam Wang

One of the more interesting post-election voices has been that of the magazine Teen Vogue. Normally one might think of Teen Vogue as being purely oriented toward culture and fashion…but the same could be said of Vanity Fair, GQ, and Rolling Stone – all of which have a strong political voice. Julian Zelizer and I interviewed Teen Vogue’s Lauren Duca, author of “Trump Is Gaslighting America.”

Listen now:

→ 2 CommentsTags: Politics

A Contest: Hack the Gerrymandering Standards!

May 20th, 2017, 5:28pm by Sam Wang

June 1: Thank you for your entries. We are evaluating them, and will post the results – as well as an explainer for what we learned – shortly.

Today I did an Ask Me Anything on Reddit Politics. In conjunction with the AMA, we have a contest! The deadline is Wednesday, May 31st.

I have developed multiple statistical tests (Stanford Law Review) to detect partisan gerrymandering. These tests are focused on the principle of partisan symmetry, a phrase that appears in Supreme Court writings. In the past, a majority of justices of the Court has expressed interest in partisan symmetry as a standard, but there was not agreement on how to identify it. This year two cases, one in Wisconsin and one in North Carolina, give them an opportunity to address this task.

We need your help to see if the simple standards can be hacked. Many standards look reasonable on paper, but a clever person may be able to come up with ways to “game” the standards to benefit their side. In this contest, we are looking for talented hackers who can evade the rules and find ways to slip through the net. If you can do that, you can help us either rule out standards that are too loose or that need to be combined with other standards to close the net. Think of it as helping us build a spam filter for gerrymandering!

The contest is here. Use this worksheet [UPDATED 5/25 10:30am] to construct your entry, and then mail it to

If there are problems with the contest, please let us know in the comments section here.

→ 33 CommentsTags: Redistricting

Politics & Polls: Falling Toward Pavement

May 18th, 2017, 1:31pm by Sam Wang

Washington has been hit with a trifecta of catastrophic events in the past week: Trump fires FBI director Comey for investigating Russian collusion with the Trump campaign, then Trump tells secrets to the Russians in the Oval Office, then it emerges that Comey writes memos about all his conversations, including Trump trying to obstruct the FBI investigation.

What’s next in the ongoing saga of the Trump presidency? Listen to this time capsule, in which Julian and I speak to you from the distant past of…yesterday at 1:15pm.

Listen now:

→ 3 CommentsTags: Politics · President · U.S. Institutions

Gerrymanders, Part 3: Redistricting Nerds, Geographic Compactness Does Not Solve Your Problems

May 14th, 2017, 4:27pm by Sam Wang

For general audiences, I have written quite a bit about gerrymandering in the New York Times (in 2013 and in 2015) and recently, in the Los Angeles Times. In addition, I have drilled into the technical details in the Stanford Law Review and here at the Princeton Election Consortium (part 1 and part 2). Today I want to discuss map-based reforms, such as the belief that requiring geographic “compactness” will solve the problem. Today I will explain why such an approach is flawed, potentially fatally. [Read more →]

→ 11 CommentsTags: Redistricting

Authoritarian Government Watch – Update

May 11th, 2017, 7:53pm by Sam Wang

On January 28th, I came up with 10 events that, if they happened, would constitute evidence of an authoritarian government. Now it’s the fourth month. As the Administration becomes engulfed by the growing Russia scandal and possible obstruction of justice by Trump himself, how are they coming along on the authoritarian front?

Actually…not that bad. [

→ 16 CommentsTags: President