What if Biden or Trump suddenly leaves the 2024 race?

What would happen if a major-party candidate died or abruptly dropped out of the presidential race before Election Day?

In any presidential election year, there could always be a sudden tragedy or scandal that takes a leading candidate or nominee out of the picture. But this question could be especially relevant in 2024, as Americans tell pollsters they're concerned about the advanced age of both the Republican and Democratic front-runners for president: 77-year-old former President Donald Trump and 81-year-old President Joe Biden.

Trump is also facing legal challenges that could theoretically force him from the race, although he has denied wrongdoing in each case and seems unlikely to bow out of the race voluntarily. (According to ABC News Chief Legal Analyst Dan Abrams, he is almost certainly not going to be disqualified under the 14th Amendment or imprisoned before the election. And even on the slight chance he is in prison, there is nothing that legally prevents him from remaining a candidate.)

Replacing a party nominee or president-elect would be messy under any circumstances, but exactly how messy depends on when the candidate drops out. At some points in the calendar, there would be a clear path forward; at others, the country would be facing an unprecedented situation — although experts say the parties have contingency plans for most such scenarios.

Here's what could happen if either party's front-runner dropped out at various points in the next year.

From now to March

Elaine Kamarck, a senior fellow at the Brookings Institution and member of the Democratic National Committee, told 538 in an interview that one of the least complicated times for a front-runner to leave the race would be right now — when no voting has started and delegates are not yet bound to candidates. "If it's now, there's still somewhat of a chance to have a real race," Kamarck said.

Indeed, if Trump were to drop out or pass away within the next couple months, Republicans have a number of well-funded, formidable alternatives, like Florida Gov. Ron DeSantis and former U.N. Ambassador Nikki Haley, who are already on primary ballots across the country and could win the nomination in Trump's stead.

But if Biden were to leave the race right now, Democrats would be in more of a bind. Very few prominent Democrats have thrown their hats in the ring against Biden, and those who have, like Rep. Dean Phillips and author Marianne Williamson, have had trouble qualifying for the ballot in certain states. Out of 28 contests with candidate lists as of Jan. 5, Phillips missed out on three while Williamson didn't make it in five, and Biden is the only candidate on the ballot in the delegate-rich states of Florida and North Carolina.

Not to mention, Phillips and Williamson would probably not be acceptable nominees for Democratic Party leaders because of their low profiles, lack of institutional support and the feathers they ruffled by challenging a sitting Democratic president. So if something happened to Biden, you could see a new Democratic candidate (or 10) try to jump into the race. But candidates who entered the race today would have no way of securing a delegate majority at the ballot box because they, too, would not appear on the ballot in many states. As of Jan. 5, the filing deadline for presidential candidates has now passed in 31 states or territories worth about two-thirds of the party's delegates.

Despite this, it wouldn't be impossible for a Democratic candidate who enters the race today to garner significant delegate support. The party could go to court to try to change filing deadlines for some primaries, or cooperative state legislatures could reschedule those deadlines — or even entire primaries. And new candidates could try to mount write-in campaigns in key states where filing has already closed, so they could still earn some delegates in those places.

However, some states don't permit write-in candidates (either generally or in primaries) or require them to register ahead of an election to have votes cast for them counted. Moreover, write-in candidates or even current contenders like Phillips and Williamson could struggle to get enough votes to reach the 15 percent of the vote that Democrats require for candidates to pick up delegates at the state or district level. Their ability to hit that 15 percent mark would depend in part on the level of support Biden attracted — he would remain on the ballot in many places — as well as whether a state has an "uncommitted" option on the ballot that voters could flock to.

In sum, it would be very difficult for any candidate to clinch a delegate majority in this scenario, meaning that the nominee would be decided at the convention.

From March to June

The period between March and June, when the majority of high-profile state primary elections have concluded, could be one of the most uncertain times for a front-runner to withdraw from the race.

It would be just about mathematically impossible for a Biden or Trump alternative to win the nomination at the ballot box if a withdrawal happened in this period. By mid-March (March 12 for Republicans, March 19 for Democrats), both parties will have allocated a majority of their delegates. As a result, even though there would still be several primaries to go, a new entrant to the race or an existing candidate who hadn't won a significant number of delegates yet* couldn't possibly win a delegate majority, and no one would go to the convention as the presumptive nominee.

At this point, all the remaining candidates could do is try to accumulate as many delegates as possible in the remaining states in order to try to win the nomination on the convention floor. To do this, though, they'd probably need support from some of the delegates allocated to Biden or Trump before they dropped out. And the rules governing these delegates vary by party.

Without a rule change, many delegates who were assigned to Biden would likely go into the Democratic convention uncommitted, Kamarck told us. (Even though she is on his ticket, they would not automatically shift to Vice President Kamala Harris: The presidential and vice presidential ballots are separate at the Democratic convention.) Unlike Republican delegates, Democratic delegates are "pledged" rather than "bound" to a candidate, and while party rules say that delegates "shall in all good conscience" reflect the views of those who elected them, Kamarck said there is no penalty if a delegate votes differently. This could make it easier for Democrats to adjust to a highly fraught situation in which the incumbent president has unexpectedly left the picture.

Meanwhile, if Trump departs the GOP race before the convention, the rules of each state Republican Party would determine whether his delegates are still bound to him and for how many ballots. If the state party doesn't have specific unbinding rules, the delegates would still be bound for at least the first round of voting, and potentially more, according to the rules of the Republican Party (though the convention delegates themselves could vote to change the rules).

This much is clear, though: In the event that Biden or Trump leaves the race this spring, individual delegates would suddenly have a lot of influence on whom their party nominates. Because of this, there could be a "mad rush" of people seeking delegate positions so that they can play kingmaker at the convention, Kamarck said. Generally, in both parties, primary voters decide only the number of delegate slots allocated to each candidate; the actual people who serve as delegates are usually not decided until later. While some are directly elected in primaries, most are selected well after, at congressional district and statewide caucus-conventions or by party committees.

Those who run to be a delegate indicate who they would support as the nominee. Traditionally, Kamarck said, candidates are "involved in putting forth slates of candidates for those congressional district delegates, because they want to make sure that people get elected who are loyal to them." This would undoubtedly be even more true if those delegates were up for grabs: Anyone running to be a delegate could be courted by swarms of candidates seeking their pledge of support. "All of a sudden these real people would be important people, right? And everybody would want to know who they are. All the people who wanted to be president would want to talk to them," Kamarck said.

Whom those delegates would likely gravitate to also probably depends on the party. Should Biden have to bow out, Harris — as Biden's running mate and, potentially, the sitting president — would be a natural, even likely, destination for many Democratic delegates. Lara Brown, a political scientist and author of "Jockeying for the American Presidency: The Political Opportunism of Aspirants," told 538 that she does not believe that the Democratic convention would be all that contested in the event Biden passed away. There could be a symbolic first ballot vote for Biden, "then essentially, [the convention could] create a point of order … and then do a second ballot," likely for Harris to be the nominee, Brown said.

For Republicans, the second-place finisher in the primaries could have a leg up. Per Kamarck, Trump delegates might be inclined to eventually support whoever performs best in the primaries after Trump's withdrawal.

From June to the conventions

What happens if a presumptive party nominee dies, withdraws or becomes incapacitated after primary voting has ended? Kamarck said the answer is straightforward. "In June, when the whole thing is over, it's very clear that it's going to the convention."

As in the first two situations, the Republican National Convention (which takes place July 15-18 in Milwaukee) or Democratic National Convention (which takes place Aug. 19-22 in Chicago) in this scenario would become a once-in-a-lifetime political spectacle. Once the delegates that had been bound to the presumptive nominee are officially uncommitted (which would happen according to the same rules described above), there would be a scramble by newly minted candidates to win their support. "There'll be some formidable candidates," Kamarck predicted. "They will start calling delegates as quickly as they possibly can."

Any new candidate who wants to run at this point would have to get nominated at the convention itself, the rules for which are different for each party. At the Democratic convention, new candidates need to get at least 300 delegate signatures in order to be nominated. For Republicans, convention rules state that candidates have to submit evidence of support from a plurality of delegates in at least five states at least one hour before names are to be placed in nomination.

The model for this kind of contested convention would be nominating contests before 1972, which is generally seen as the start of the modern presidential nomination system. Before then, party insiders dominated the delegate selection process in most states, and primaries (when they were held) chose far fewer delegates. Primaries instead mainly served as an opportunity for candidates to prove to uncommitted party leaders that they could win votes in a general election.

One notable contested convention came in 1968, when Vice President Hubert Humphrey won the Democratic nomination without having entered a single primary. That convention, with its chaotic protests, police rioting and internal party divisions over the Vietnam War and other issues, helped precipitate the reforms that led to the modern primary process as we know it today. For Republicans, the 1952 convention battle between General Dwight Eisenhower and the more conservative Ohio Sen. Robert Taft stands out. Eisenhower narrowly led Taft on the first ballot, but he stood just short of a delegate majority when Minnesota delegates began a tide of vote-switching to Eisenhower that clinched the nomination for him.

In the most chaotic scenarios, it could even take more than one ballot for a candidate to win a majority of delegates and clinch the presidential nomination. The last time a major party needed more than one ballot to nominate a presidential candidate was in 1952, when Democrats took three ballots to choose Illinois Gov. Adlai Stevenson as their standard bearer.

From the conventions to when ballots are printed

The national conventions are a key turning point in our hypothetical calendar. Before them, primary voters, or delegates selected through the primary process, would still have the ability to choose their party's nominee. After the conventions, though, the Democratic and Republican national committees would inherit that power.

Both the DNC and the RNC have enshrined in their rules a process for how to fill a vacancy on the party's ticket after the formal nomination has already taken place. For Democrats, there is only one option: Chairman Jamie Harrison would confer with Democratic leadership in Congress and the Democratic Governors Association and would then take the decision to the DNC, according to the party's call to convention.

The 483 members of the DNC — who comprise the chairs and vice chairs of each state Democratic Party committee as well as members elected from all 56 states and territories, plus Democrats Abroad — would vote on a new nominee. There are no rules governing who the nominee has to be; the nomination would not, for instance, just go to the former nominee's running mate or the person who won the second-most delegates in the primaries. They just need to get a majority of party members to vote for them.

Experts say that could be a political mess, with various factions of the party pressuring members to choose one nominee or another. "They would have all sorts of internal politicking. There would be competition between various factions within the party," Richard Pildes, a professor of constitutional law at New York University Law School, told 538.

For their part, Republicans have two options for filling a vacancy, according to the party's rules. Like the Democrats, they could choose to have their committee members vote. There are three RNC members per state and territory, but they get to cast the same number of votes their state or territory's delegation was entitled to cast during the Republican National Convention. If members of a delegation aren't in agreement on who to support, their state or territory's votes would be divided equally among them. In order to become the nominee, a candidate must secure a majority of votes.

But the RNC is also "authorized and empowered to fill any and all vacancies" by reconvening the national convention.

In either case, the results of all of the primaries and caucuses would no longer formally matter. While the primary results would be one source of information for the members (if they vote) or delegates (if they reconvene the convention), they wouldn't be bound to choose the person who came in second in the primaries. They don't even have to choose somebody who ran in the primary.

Beyond their distinct rules, Pildes did not think there would be much difference between how Democrats and Republicans would deal with a candidate's death. The RNC is much smaller than the DNC, which could have an impact. "It's always easier to reach decisions in a smaller body than a larger body, and so that might be a significant difference in the way the two parties are governed," Pildes said. "But other than that, I don't think there's a dramatic difference."

From when ballots are printed to Election Day

However, if either party nominee dropped out or passed away after ballots were printed, then it would be too late to officially replace them on the ballot. In that scenario, millions of Americans would cast ballots for the inactive candidate with the understanding that their Electoral College votes would really go to someone else — probably someone designated by the DNC or RNC.

"The reality is, when you vote for president, you're never voting for that person. You're voting for the elector to cast a ballot for that person at the Electoral College meeting in December," Brown said. "I would imagine what would happen is that parties would indicate to the electors who they should vote for."

From Election Day to Dec. 17

Next, let's say we make it to Election Day without incident and voters choose a new president — but then the president-elect passes away or becomes incapacitated before the Electoral College votes on Dec. 17 to make their win official. This could be a messy political situation as well.

According to the National Archives, there is no prescribed process for what to do if the president-elect dies between Election Day and the meeting of the Electoral College. (It would not automatically be the vice president-elect, as, legally, the presidential line of succession would not have kicked in yet.) So the (ex-)president-elect's electors would essentially get to pick the president. "A whole bunch of Americans don't realize that the electors are actual, real live people," Kamarck said, who could theoretically choose for themselves whom to vote for.

There is historical precedent for this: After the 1872 election, which was won by Republican Ulysses S. Grant, Democratic nominee Horace Greeley died on Nov. 29, and his electors' votes went to various other people. According to Pildes, whether this could happen again depends on the state, as some state laws address this possibility while others do not.

There have also historically been "faithless electors" who have not voted for the candidate who won their state. Some states have laws prohibiting this, but in an emergency situation, state legislatures could change the rules to allow them to do so.

It's possible that the party would coalesce around a new candidate (for example, the vice president-elect would be a logical choice) and its electors would vote en masse for that person. Brown said the DNC or RNC would likely signal to electors whom they should vote for. That could be Harris on the Democratic side or Trump's still-unannounced running mate on the Republican side. But Brown emphasized that some states would need to adjust their faithless electors laws to allow for this.

If the electors cannot agree on a single alternative and no candidate gets a majority of electoral votes, the election would fall to the House of Representatives — a procedure known as a contingent election. The Constitution stipulates that each state's House delegation would cast a single vote for president, with a majority of states required for a candidate to win, and the Senate would elect a vice president based on a majority vote of its members individually. But Brown said that this is a highly unlikely scenario, as the electors would most likely listen to guidance from their party.

From Dec. 17 to Jan. 20

If the president-elect dies or is incapacitated after the Electoral College votes but before Inauguration Day on Jan. 20, 2025, the law is clear: the vice president-elect would be inaugurated instead. The 20th Amendment to the Constitution says, in part, "If, at the time fixed for the beginning of the term of the President, the President elect shall have died, the Vice President elect shall become President."

Conclusion

All of the ballot, delegate, convention and party machinations outlined above get very "in the weeds," as Kamarck put it. Yet if Biden or Trump were to pass away or abruptly withdraw from the 2024 presidential race — or if a nominee did so in a future election — every last detail would matter deeply. And that's aside from the potentially intense reaction from the American public; people would understandably be uncertain about what comes next.

At the same time, no experts who spoke with 538 framed a nominee's sudden death or withdrawal as an alarming possibility or constitutional crisis. Brown said she does not believe a major candidate passing away would greatly destabilize American politics, because of how much is laid out in the Constitution and in the party rules already.

"Just because these things have not happened in modern times, because the parties and the candidates have essentially coordinated to ensure more predictable outcomes, doesn't mean that if we went to the contingency plan, that our system is lost," Brown said. "We're just in plan B — and plan B usually isn't optimal. But it is serviceable."

Footnotes

*This whole exercise is predicated on the assumption that Biden and Trump will win the vast majority of delegates as long as they are in the race. Obviously, if this is not true and a candidate like Haley is, say, roughly tied with Trump in delegates on March 12, they would still be able to win the nomination the traditional way.