It’s very unlikely — but theoretically possible — that the presidential election ends with a 269-269 tie in the Electoral College.

That would mean that neither Kamala Harris nor Donald Trump, who are locked in a toss-up race, wins enough electoral votes to become president.

This hasn’t happened in modern American politics — it did happen back in 1800 — and after a renewed effort to change how Nebraska allocates its electoral votes failed, it is now looking even less likely that a tie would occur.

But if this year’s election did end 269-269, the U.S. Constitution does have a plan for what happens next. Experts and scholars point to Article II of the Constitution as well as the 12th Amendment to outline how this would work.

Elaine Kamarck, a senior fellow at the Brookings Institution who has written a lot about presidential elections and presidential nominations, said we “have a pretty good rulebook” for where things go if there is a tie.

Ultimately, she said, the election moves to the U.S. House of Representatives, where the newly elected members of Congress would have to be sworn in and then vote on who becomes president.

The way this would work is that each state — regardless of the size of the state’s delegation — gets one vote.

“I don’t know if they would deliberate or not or just take a poll,” Kamarck said. “In some cases, it’d be pretty easy. And they would cast their vote for one of the people who finished in the Electoral College.”

Because it is unlikely third-party candidates will win any electoral votes this year, each state would have to vote for either Trump or Harris.

“The Constitution says you need a majority of the House delegations,” Kamarck said. “So that would be 26 House delegations.”

Republicans currently have an edge if it were to come to this, because the party right now has control of 26 U.S. House delegations and Democrats control 22 delegations. Two states — Minnesota and North Carolina — have split delegations. This, of course, could all change depending on what happens in this year’s general election.

“What we’re really saying here is if the Electoral College was really in a tie, then the outcome of House races and Senate races would be absolutely critical to the outcome of the [presidential] election,” Kamarck said.

She mentioned the U.S. Senate because a similar process would play out there to decide who would become vice president. In that case, though, each senator gets a vote — instead of one vote per state like in the House. The candidate that gets to 51 votes becomes the vice president. And because these are separate votes, it is possible that the president and vice president could end up being from different political parties.

If the House can’t get to 26 votes for a presidential candidate the first time, they would have to keep voting.

And if no candidate gets to 26 by Inauguration Day, the person chosen as vice president by the Senate will be acting president while the House continues to vote.

“The House keeps voting and voting until the tie is broken,” Kamarck said. “So, there is an end to it.”