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NORTON META TAG
08 November 2016
Daily Kos Elections final presidential forecast: Clinton 323 electoral votes, Trump 215 8NOV16
Over the course of this presidential campaign, Daily Kos Elections has logged 1,371 state-level presidential polls into our database. All signs point to a Hillary Clinton victory.
Our forecasting model indicates that Clinton is highly likely to win key states includingColorado, Pennsylvania, New Hampshire, Virginia, and Wisconsin. In all five of these states, Clinton has never trailed in our average of the polls—and if she carries all of them, she would win the election over Donald Trump with 273 electoral votes, three more than the 270 required for victory. In addition, our model also favors Clinton inFlorida, North Carolina, and Nevada. Together, those states contribute another 50 electoral votes.
That gives us our final prediction: Clinton 323 electoral votes, Trump 215.
Given that the forecast is based almost entirely on public polling data, how much can we trust the accuracy of the polls? As recently as one week ago, Clinton held such a commanding lead that our model placed her chances of winning as high as 96 percent. Since then, the race has tightened, and we currently estimate Clinton's odds of victory at 88 percent. That's enough of a change that a large and consistent polling error could make the difference for Trump. But the error would have to be very large, and very consistent. Going into Election Day, Clinton’s average lead in the polls is 3 points in New Hampshire, 4 points in Colorado and Pennsylvania, and 5 points in Wisconsin and Virginia.
Polling is never perfect, but systematic errors across multiple states in the same presidential election are historically not that large, or that common. Instead, the state-level errors form a distribution: In some states, one candidate outperforms the polls, and in other states, the other candidate does better. For example, in 2012, on average, the polls underestimated Obama’s vote share by a small amount; nevertheless, in 22 states, his polling was higher than his eventual vote share. Polling errors are less “correlated” across states than you might expect.
What about the magnitude of the state-level polling errors?
Aggregating public polls usually produces forecasts that are very close to the actual outcome, especially in competitive states where pollsters have conducted larger numbers of polls. Again using 2012 as an example, there were 15 close states where a candidate won by 10 points or fewer (counting only the major-party vote). In seven of those states, the polls accurately predicted the margin of victory to within 1 percentage point. In another three states, the polls missed the actual margin of victory by under 2 points, and in four states, the polls were off by between 2 and 3 points. In only one state did the polls miss the margin by more than 3 points. And to reinforce our point above about correlated polling errors, Obama outperformed his polls in eight of the 15 close states; in the other seven states, Romney did better than expected.
So, while it's possible for Trump to defy the polls and win the election, it is not likely. Our model estimates Trump’s chances at around 12 percent.
Stepping away from the polling data, there are reasons to think that the probability of a Trump victory isn’t even this high. None of these other factors are formally built into our model, and I haven’t analyzed them in any systematic or historical context, but consider everything below here informed conjecture. My Daily Kos colleague Stephen Wolf also examined some of these factors, and others, in a recent post exploring why the polls could be off.
Our model also does not incorporate data on early voting, beyond what is implicitly captured by polls that include respondents who have already voted. Although there isdisagreement about how much should beread into early vote totals, one state stands out: Nevada. Heavy Latino turnout in the Nevada early voting period appears to haveput a significant dent in Trump’s chances of winning there—a must-win state for him where polls alone suggest he has at least a one-in-three chance of winning.
Finally, although the “fundamentals” of the presidential election have long beenfactored out of our forecast in favor of newer polling data, two key structural factorshave actually gotten better for Clinton over the course of the campaign: President Obama’s job approval rating is on an upswing, and the national economy is growing at a faster rate than when we first accounted for these factors back in June.
There is one last caveat that gives me pause: The number of voters telling pollsters that they are still undecided, or are intending to vote for a third-party candidate, remains unusually high. We know that these respondents are disproportionatelyyounger, white voters who would otherwise be likely to support Hillary Clinton. But we have no way of knowing for sure how these individuals will vote, or if they will turn out to vote at all. It’s something that I will be looking out for on Tuesday.