The pandemic has undermined the one major advantage exit polls have over other kinds of polls: their ability to survey only actual voters, since exit polls catch respondents as they exit polling locations. But in 2020, far fewer people will be voting in person on Election Day than in previous years; according to data from political scientist Michael McDonald, more than 93 million people nationwide have already cast an absentee or in-person early vote. That means that interviewing voters as they leave polling places on Election Day won’t give a reliable estimate of how people will vote, especially as the people waiting until Nov. 3 are likely to skew more Republican than the electorate as a whole.
To account for this, Edison Research — the polling firm that produces the exit polls used by ABC News, CBS News, CNN and NBC News — has changed its methodology so that the “exit polls” you see on Nov. 3 will actually be a combination of traditional exit polls of Election Day voters and phone polls of mail voters. In certain states, there will also be exit polls of early in-person voters, conducted at early-voting locations in essentially the same way as traditional exit polls (just conducted earlier).
But exit polls will still be less reliable this year because the phone poll and the early exit poll are much tougher to get right than the traditional exit poll.