Election workers have a long week ahead of them. Back in 2020, the presidential race was called four days after Election Day. 

We likely won’t know who officially won the 2024 race tonight either. But we will probably know before Saturday, said Robert Stein, a political science professor at Rice University who’s an expert on elections. 

More than 85 million Americans have voted early, according to a tracker from the University of Florida’s Election Lab. Over 46 million of those early votes were cast in person, while over 39 million came from mail-in ballots. It can take a while to process mail-in ballots because of how labor intensive it is.

“Processing typically involves verifying the voter’s information and eligibility on the mail ballot envelope, opening the envelope, and removing the ballot so it is ready to be tabulated by a voting machine,” according to the Brennan Center for Justice. 

There are 43 states that do allow election workers to process ballots before Election Day, but some of the ones that don’t are swing states that may decide the election. 

There are seven states considered to be competitive, which include Arizona, Georgia, Michigan, Nevada, North Carolina, Pennsylvania and Wisconsin, Stein said. 

With the exception of North Carolina, Biden won all of those states in 2020. However, those states, except for Nevada, voted for Trump over Hillary Clinton in 2016.

Although North Carolina typically goes red, Trump won the state narrowly in 2016, while former President Barack Obama won back in 2008. And while Democrats won Nevada in recent presidential elections, they did so narrowly.

Pennsylvania and Wisconsin can’t process absentee or mail ballots before Election Day. Some Pennsylvania counties also lack more sophisticated equipment to process votes faster, Stein said. 

Wisconsin’s election system also happens to be decentralized, with more than 1,900 clerks who have to handle the results, according to the Wisconsin Examiner. 

And in states with tight races, more votes need to be tallied in order to call the winner. 

PBS has a list of what time the polls close in each state available here.