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Nate Silver On Why FiveThirtyEight Forecasts A Clinton Win

Before the 2012 presidential election, statistician Nate Silver correctly predicted the presidential winner in all 50 states, proving wrong other polling firms that were underestimating then-candidate Barack Obama’s performance.

This week, Silver’s polling-analysis website FiveThirtyEight has Hillary Clinton’s chances of winning the presidency at 83.4 percent to Donald Trump’s 16.6 percent.

Morning Shift’s Tony Sarabia spoke with Silver Monday to break down the science of political polling and how this election may be upending some of the theory.

Q: You had a piece on FiveThirtyEight Monday where you basically said the second presidential debate probably didn’t help Donald Trump — and he needed the help. Can you expound on that?

A: Before the debate — and we should really say before the weekend, because it wasn’t clear as of Sunday what the impact of the tape being released was — but Trump came in down five or six points to Clinton nationally and that corresponded to some pretty big deficits in the swing states. That’s not a very good position. Our forecast gave him only a 20 percent chance to win with numbers like those. Others were even lower: five or ten percent.

So if he had a draw in the debate, even that wouldn’t be all that helpful. Post-debate polls — the scientific ones — show that voters thought Clinton did better in the debate. But it’s kind of like if you’re down two goals late in a hockey game and you exchange goals with your opponent, it doesn’t really help all that much. His position is fairly dire and at best it seems like he squandered an opportunity to turn the race around.

The point is that, suppose he had an okay debate and he made it a four- or five-point race instead of a six-point race? That’s still a fairly bad position. It’s winnable maybe. But things have gone from Trump actually having pulled pretty close before the first debate to some of the worst two-week stretches I can remember in presidential campaign history.

Q: When you look at national polls the two candidates are very, very close. Yet FiveThirtyEight gives Hillary Clinton more than an 80 percent chance of winning. What is that based on?

A: It’s based on data. It’s based on history. It’s based on saying, “When a candidate has a five or six point-lead” — and in this case it’s reinforced both by state polls and by national polls — “how often does that lead hold up?”

You could do the same thing by saying: Let’s say the Bulls have an eight-point lead with three minutes to play in a basketball game. Go back to history and evaluate how often does that translate to a win. That’s the whole principle here. So it’s not me subjectively telling you that it’s 80 percent. Frankly, after the events of the weekend, I think 80 percent might be low instead of high — my subjective take. But this is based on objective analysis of polling in presidential elections dating back to 1972.

Q: Why do we see some polls that say something that could favor one candidate and then the campaign might tout another set of polls that show something else?

A: Let’s not use the term online polls to describe the junk science that the Trump campaign was peddling after the first debate. These are little surveys that are voluntary surveys. People can spam these surveys and they should not be mentioned in the same breath as scientific polls, and the Trump people know better than that. There are some people in that campaign that are sane enough to know those polls are B.S. All the scientific polls showed after the first debate that Clinton had won by a pretty emphatic margin. The two scientific polls after the second debate on Sunday also showed a Clinton win but more of a marginal win, so you can debate what effect that will have on the head-to-head polls.

There is legitimate disagreement among polls. And to some extent that’s good. It’s a unique and interesting election. It’s good when pollsters are trying to use different methods and come to different conclusions. People should be comfortable with some disagreement. That’s healthy. But that’s different from fake “polls” that are voluntary surveys that don’t have any scientific basis whatsoever.

Q: I want to switch gears before I let you go. You said that the Chicago Cubs probably won’t win the World Series. Why not in your estimation?

A: This is one of those things where we actually have them as the favorite to win the World Series, but it’s still a case where they have to win three series in a row. They’re obviously doing well in the NLDS so far, and baseball is a random enough sport where — nevermind any curses or anything like that — it’s hard to win three series in a row. They are at the point now where I think we have them at a 35 percent chance or something and rising obviously. And we also have them as being one of the 25 or 30 best regular season teams in history by our measures.

So we’re not saying this Cubs team isn’t terrific. It’s a terrific baseball team. It’s just a lot of things can go wrong when you have to win a bunch of short series.

This interview has been edited for clarity and brevity. Click the ‘Play’ button above to listen to the entire segment.

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