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Wed Jul 13, 2016, 10:44 PM


Nate Silver: When To Freak Out About Shocking New Polls

Jul 13, 2016 at 6:48 PM

At 6 this morning, Quinnipiac University released a set of surveys of Florida, Ohio and Pennsylvania with the best polling news Donald Trump has gotten in a long time. In the version of the polls that includes third-party candidates — that’s the version FiveThirtyEight uses — Trump led Hillary Clinton by 5 percentage points in Florida, 1 percentage point in Ohio and 6 percentage points in Pennsylvania.

The results run in contrast to the preponderance of national polls, which show Clinton ahead by roughly 5 percentage points, on average. And some of the other polls released today weren’t as bad for Clinton. Some were even good for her, in fact. A Monmouth University poll showed her up by 13 percentage points in Colorado, while Fox News had her up by 9 points there. And a Marist College poll, contradicting Quinnipiac, had her up 8 points in Pennsylvania.

Nonetheless, the bevy of state polls today worked strongly to Trump’s benefit overall. His chances of winning the Electoral College are up to 29 percent, from 23 percent on Tuesday, according to our polls-only model. And they’re now 33 percent, up from 27 percent, in our polls-plus model, which also accounts for economic conditions. FiveThirtyEight’s forecasts are generally conservative until late in the race, so those qualify as fairly big changes by our standards.

Ordinarily, this is the point at which I’d urge a little patience. There’s been a lot of news over the past two weeks — the conclusion to the FBI’s investigation into Clinton’s emails and the Dallas shootings of police officers, in particular — and it would be nice to see how the polls settled in after a couple of slow weeks on the campaign trail. However, we’re entering a period of rapidly moving political news. Bernie Sanders endorsed Clinton only Tuesday. Trump is expected to name his VP later this week. And then we’ll have the party conventions. The prospects definitely look better for Trump than they did a week or two ago, but the landscape also looks blurrier, and it may not be until mid-August that we have a chance to catch our breath.

So for the rest of this article, I’m going to focus mostly on the Quinnipiac polls — both to explain why our model reacted relatively strongly to them, when some of the other data wasn’t so bad for Clinton, and as an example of how you might think about “unexpected” polling results as they arise over the next few weeks. If you’re a poll junkie, this situation will seem familiar. You think you have a pretty good idea of where the race stands, but then a couple of splashy polls come out that contradict that impression. You have to figure out how much to incorporate the new polls with the data you had previously.


Great analysis!

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