As voters head to the polls for the 2024 election, there remains a possible but unlikely scenario that Vice President Kamala Harris and former President Donald Trump end up tied in the Electoral College.

Thanks to 23rd Amendmentwhich gives electors to the District of Columbia, there are 538 votes in the Electoral College. Because it is an even number, it is mathematically possible that the election could end in a tie of 269-269, one short of the 270 needed to win the presidency.

Possible does not mean probable. There has only been one Electoral College tie in history, and the last time a candidate didn’t win the Electoral College was 200 years ago. But there are a few potential scenarios that could result in Harris and Trump each getting 269 Electoral College votes.

Here’s everything you need to know about what happens in the event of a tie in the Electoral College.

What is the Electoral College and how is the number of votes determined?

The Electoral College is the constitutionally established process for electing the president and vice president every four years, which the Founding Fathers viewed as a compromise between direct election by popular vote and selection of positions by Congress. It was also intended to benefit the Southern Stateswho gained additional representation in Congress based on their slave population.

There are 538 total electors spread across all 50 states and the District of Columbia. States get two votes for each senator and one vote for each member of the House of Representatives. Pennsylvania – with two senators and 17 representatives – therefore has 19 votes.

Two states – Nebraska and Maine – distributed their electoral votes by congressional district.

To win the presidency, a candidate must receive 270 electoral votes, or “a majority of the whole number of electors appointed,” as required by the Constitution.

What are the scenarios in which Harris and Trump could find themselves tied?

Here are three scenarios in which the election could end in a 269-269 electoral college:

First scenario

Trump wins the so-called “Blue Wall” states of Pennsylvania and Michigan, no longer Georgia, but Harris keeps Wisconsin and wins Arizona, Nevada and North Carolina.

Second scenario

Trump won the three “Blue Wall” states – Pennsylvania, Michigan and Wisconsin – as well as Nevada, but Harris won North Carolina, Georgia and Arizona.

Third scenario

Trump won Pennsylvania, Michigan and North Carolina, but Harris held on to Wisconsin and won Georgia, Arizona and Nevada.

Who becomes president in the event of a tie in the electoral college?

As stated in the 12th Amendment, if there is a tie in the Electoral College (or if one candidate does not receive a majority of votes, perhaps due to third-party candidates), the presidential election would move to the House, where each state’s congressional delegation would get one vote.

To win the presidency, a candidate would need to obtain 26 votes. In this scenario, the District of Columbia would not get a vote because it is not a state.

Republicans control 26 state delegations, while Democrats have a majority of 22 delegations. Two states have delegations composed equally of Republicans and Democrats: Minnesota and North Carolina. If a state’s delegation is deadlocked, it will not get a vote.

However, it would be the new Congress elected on November 5 that would break the tie in the Electoral College. So if Democrats pick up seats in the 2024 elections, that could give Harris a better chance of winning the presidency with a slim chance of a tie.

The vice president would be chosen by a simple majority vote in the Senate, currently controlled by Democrats. So it’s possible that you’ll see a president and vice president from different parties if there’s a tie in the Electoral College.

Have there ever been ties in the Electoral College?

Just once. In 1800, Thomas Jefferson and Aaron Burr tied in the Electoral College. It went to the House, which ultimately chose Jefferson as president and Burr as vice president.

In the presidential election of 1824, no candidate received a majority of the electoral votes. Andrew Jackson received the highest number with 99, but that was 32 short of the number required at the time to win the presidency. John Quincy Adams received 84 electoral votes, 15 fewer than Jackson, but was chosen by the House and was ultimately elected president.