AUDIE CORNISH, HOST:
Here are two words we'll hear a lot tomorrow - exit poll. Exit polling is how we get the data used to estimate election results before the official tally is in. But where do exit polls come from, and what can they tell us? The NPR Politics Podcast team is all over it.
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SAM SANDERS, BYLINE: I'm Sam Sanders, campaign reporter.
DANIELLE KURTZLEBEN, BYLINE: I'm Danielle Kurtzleben, political reporter.
DOMENICO MONTANARO, BYLINE: I'm Domenico Montanaro, political editor.
SANDERS: And we have a special guest with us from the Pew Research Center - Courtney Kennedy, director of survey research there. Hi, Courtney.
COURTNEY KENNEDY: Hi.
SANDERS: What will be happening behind the scenes out in those states giving us that data while we're watching?
KENNEDY: Because there's so much early voting, there's really two major components to what we call the exit poll. The first is a national telephone poll that's going on right now to capture people that have already voted or that say they definitely will vote before Election Day. So you can't get those people obviously in person at a precinct, so you've got to get them. We do it on the telephone.
And then separately on Election Day, there are people that are assigned to sample precincts across the country that interview people as they're leaving the polling place.
SANDERS: So is there a good chance that you will actually see an exit poller if you're voting on Tuesday?
KENNEDY: It's a very small probability when you...
SANDERS: OK.
KENNEDY: ...The millions of people that will be voting. And the way it works is not actually, like, just sort of exiting the voting booth in particular but more exiting the premises, sort of walking out to your car or walking back to your home. Once you're off site of the facility, then the exit poller randomly samples voters.
And to tack onto that, this is information that Edison Research, which does the exit polling, gave me earlier this year. We cited it in an earlier podcast with superfans. They do 900 to a thousand polling sites, and they hit about a hundred thousand to 130,000 people. And yeah - out of - what? - 120-some million voted in 2012 - something like that.
KURTZLEBEN: That's right.
KENNEDY: Yeah, so it's a tiny, tiny, tiny...
SANDERS: Yes.
KENNEDY: ...Tiny sliver.
SANDERS: Yeah.
MONTANARO: So big picture for me here - you know, should we trust exit polls? I mean they've been wrong in the past. There's been some error in them. But overall should we trust exit polls?
KENNEDY: Yes. I mean - and you have to keep in mind, too...
SANDERS: You have to say that.
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KENNEDY: Well, no. Well, think of the alternative. I mean the exit polls - there's two things that happen on election night, and people often conflate them. So there is one process where people are calling winners of races, right?
SANDERS: Yes.
KENNEDY: And that's often called the decision desk. And all of the major news outlets have a decision desk that...
SANDERS: Yes.
KENNEDY: ...Are calling races. And that's based on, you know, these historical models and also the data that are coming in that day, right? And then separately you have the exit poll. And the exit poll is used to talk about who voted for which candidates and why. And those data are weighted to adjust for the potential problems in terms of non-response and so forth. And after weighting, they're generally quite good.
It is interesting that, you know, over the course of the evening there's different rounds of weighting. So it's possible that those estimates change throughout the night, but they - they're usually not changing wildly.
SANDERS: Well, I'll tell you what poll does matter. The only one that matters is the one on Election Day.
MONTANARO: Oh.
SANDERS: On that note...
KURTZLEBEN: Yeah.
MONTANARO: Boy.
SANDERS: Thank you so much for your time today. I learned a lot. I'm Sam Sanders, campaign reporter.
KURTZLEBEN: I'm Danielle Kurtzleben, political reporter.
MONTANARO: I'm Domenico Montanaro, political editor.
KENNEDY: Courtney Kennedy, director of survey research, Pew Research Center.
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CORNISH: And that's the NPR politics podcast team.
ARI SHAPIRO, HOST:
The day you have been waiting for or dreading is almost here. Listen to NPR tomorrow night and Wednesday morning. We will be live on air through the night, breaking down national and local election results. Listen here and follow the races important to you at npr.org. Transcript provided by NPR, Copyright NPR.