Why early vote trends can't tell you who will win an election

Be careful trying to translate early and absentee voting statistics into trying to determine the winner of the presidential election.


Related video above: Early voting underway at Fenway Park

You've seen the pictures of early voting lines out the door. You may have read the stats of the high number of voters requesting absentee ballots.

But be careful trying to translate early and absentee voting statistics into trying to understand whether President Donald Trump or former Vice President Joe Biden is going to win the presidential race.

We know from the polls that a record number of people will probably be casting a ballot before Election Day this year.

Those same polls indicate there will be a massive difference between the percentage of Biden and Trump supporters who will vote early. Biden supporters are much likely to cast an early ballot.

In an ABC News/Washington Post poll conducted late last month, Biden was ahead of Trump by 36 points among those voting before Election Day, while Trump was up by 19 points among those who said they'd vote on Election Day.

But it's hard to know the extent to which the early vote will be more Democratic-leaning than the overall tally. There's no history of early voting during a pandemic. Moreover, just because we know the party affiliation of the voters returning ballots in some states doesn't mean we know whom they're voting for.

In 2016, a year in which the partisan split between early and Election Day voters was much smaller, Hillary Clinton won voters who cast their ballots before Election Day in two pivotal battlegrounds: Florida and North Carolina.

But it was Trump who won overwhelmingly with Election Day voters and carried both states.

A similar situation might unfold in Florida this year. A lot more Democrats are voting early in Florida than Republicans, while Republicans seem to want to wait in the Sunshine State.

None of this is to say early voting statistics are useless. They're telling us that the polls seem to be on the right track. There are a lot more people voting early than ever before, and these folks tend to be Democrats.