Princeton Election Consortium

A first draft of electoral history. Since 2004

The 2016 Senate Forecast (open comment period)

August 29th, 2016, 12:00pm by Sam Wang

Close readers of the Princeton Election Consortium know that we calculate not only a snapshot of current Senate conditions, but also predictions of final outcomes. Last week, Josh Katz at The New York Times’s The Upshot started publishing a comparison of models, including PEC’s. Today, I start featuring it in the banner above.

Today, according to our model, Democrats have a 72% chance of winning the Senate. Because the probability of Senate control is in the 20-80% midrange, it is currently an important place for both sides to put resources, Democrats through ActBlue and Republicans through the NRSC.

I will explain PEC’s Senate model. It uses the same math as the Presidential forecast, and consists of three steps:

  1. Taking a snapshot of current Senate conditions and calculating a Meta-Margin (MM);
  2. Projecting random drift in MM; and
  3. Filtering that projection through a separate prior to make a November prediction.

This probability calculation depends most strongly on one parameter, the overall movement in conditions between now and Election Day. This approach has the virtue of simplicity. In models of greater complexity, future change has to be estimated in multiple ways, which may excessively compound the uncertainty of the prediction. In the PEC approach, good estimation of a few parameters gives a prediction that is as confident as possible based on data. However, these few parameters must still be estimated accurately!

Step 3 above is new and represents a substantial improvement over the 2014 forecast. I will describe why that election’s lessons have led me to use a non-polling prior. This is going to be technical; the most gory details, which can be skipped, are in italics. [Read more →]

→ 22 CommentsTags: 2016 Election · Senate

Politics And Polls #9: Top Three Moments of Campaign 2016 (so far)

August 25th, 2016, 5:00pm by Sam Wang

On Politics & Polls (SoundCloud, PodOmatic, and iTunes): Julian Zelizer and I chew over three pivotal moments in Campaign 2016. Also, I finger what I think is one remaining big moment. Hint: rhymes with Mouse of Mepresentatives. Listen now!

Comments OffTags: 2016 Election

Sharpening the Presidential Forecast – summary of comments

August 24th, 2016, 10:00am by Sam Wang

Comments on my sharpening of the Presidential forecast were helpful. The outcome is that I will keep the key new assumption, which is to cap future standard deviation in the Meta-Margin at 3.0%. Since Hillary Clinton’s Meta-Margin (effective popular lead, measured through Electoral College mechanisms) is 6.3%, that means that she is 2.1 standard deviations ahead. That is a lot of standard deviations.

A summary of the discussion follows. I will start with the key graph, which I produced in response to Joel. Like all my analysis of the 1952-2012 elections, this was made using Wlezien and Erikson’s data. Prof. Wlezien has helpfully provided the original dataset on his website.
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→ 69 CommentsTags: 2016 Election · President

Sharpening the 2016 Presidential Forecast

August 21st, 2016, 2:47am by Sam Wang

Today I present a beta version of the sharpened forecast. In May, I said that I would update the model after the dynamics of this year’s race became clear. Back then, I wondered whether the 2016 campaign would be more like 1952-1992 (high variability), or like 1996-2012 (low variability). This year’s data indicate that it is the latter – opinion is relatively stable. That stability affects the November forecast.

This is an open comment period. Technical feedback is welcome. (The comments section is rather good this time.) [Read more →]

→ 100 CommentsTags: 2004 Election · 2008 Election · 2012 Election · 2016 Election · President

Politics & Polls #8: How To Interpret Polls

August 18th, 2016, 9:36pm by Sam Wang

On Politics & Polls (SoundCloud, PodOmatic, and the slower-to-update iTunes): Julian Zelizer and I offer up a basic primer on how to make sense of the onslaught of polls. What should we think of a really surprising result? Are polling numbers twisting and turning with every week’s news…or are polls the best empirical measure we can count on in a crazy year? Want to learn a trick for aggregating polls that is so simple that it does not even involve arithmetic? All this and more…listen now!

→ 23 CommentsTags: 2016 Election

The Electoral Strike Zone (technical announcement)

August 18th, 2016, 8:00am by Sam Wang

Here at PEC, the likely range of electoral votes is set by assuming that opinion can drift in either direction, by an equal amount across states; and then converting that swing into electoral votes. This generates the red “strike zone” in the plots in the right sidebar. Today I make a small update. [Read more →]

→ 6 CommentsTags: 2016 Election · President

In state polls, Clinton running 5.8 percentage points ahead of Obama 2012

August 16th, 2016, 5:41pm by Sam Wang

There is a lot of media drooling over polls showing Donald Trump cratering in state after state. I find this gloating to be unseemly. Here at PEC, you can do all your gloating in one go, saving time for other reactions, like schadenfreude.

Plotted below are median Clinton-minus-Trump margins in all states for which August polling is available, plotted against Obama-over-Romney margins at the same point in the 2012 campaign. This horizontal axis quantity is better to plot than the final Obama-Romney election margins, which include undecided voters’ final commitments – not a fair comparison.

The data come from RealClearPolitics.

Clinton is overperforming Obama in 15 out of 17 states, the significant exceptions [Read more →]

→ 105 CommentsTags: 2012 Election · 2016 Election · President

What do polls and neuroscience have in common?

August 16th, 2016, 10:43am by Sam Wang

Find out in a profile published yesterday on the University’s homepage. Bonus: it may be the only time you will ever find the cerebellum and gerrymandering mentioned in the same article.

→ 5 CommentsTags: 2014 Election

Today on The Takeaway: Who Is Evan McMullin, And Why Is He Really Running for President?

August 15th, 2016, 8:15am by Sam Wang

Today on The Takeaway, I discuss the impact of Evan McMullin’s entry into the Presidential race. His biggest effect will be downticket, where control of Congress is in the balance. The basic evidence: McMullin is a House GOP staffer, not a politician; and for every 1% of Republican turnout that he can salvage, they can recover up to six House seats – which could be crucial in determining control. As of this weekend, McMullin will be on the ballot in Colorado and Minnesota, where six swing districts are on the line (CO-03, CO-06, MN-01, MN-02, MN-03, and MN-08).

The show airs nationwide at various times starting at 9:00am Eastern. Find a radio station near you, or listen to it here.

Incidentally, activists on both sides are turning their attention to downticket races. Democrats, see ActBlue. Republicans, see the NRSC.

→ 22 CommentsTags: 2016 Election

Get PEC pushed to your mobile!

August 13th, 2016, 8:00am by Sam Wang

The Princeton Election Consortium is partnering with StatX to bring to you a way to get our data updates automatically. The StatX app can provide you with all the key outputs on our calculations, updated five times a day: the EV snapshot, current Senate and House estimates, and the Meta-Margins. The app will link back to this website so you can get full site content.

You will need the free StatX app on your iPhone or Android (or search statx in Apple App Store or Google Play Store). Give it a try! Send any StatX-related suggestions and feedback to Below, some answers regarding privacy concerns… [Read more →]

→ 17 CommentsTags: 2016 Election · Site News