What happens if Joe Biden or Donald Trump drops out of the presidential race?

What happens if Joe Biden or Donald Trump drops out of the presidential race?

Ahead of the first 2024 US presidential debate on Thursday, voters remain concerned about the candidates’ fitness for office.

Joe Biden, 81, must use the debate to convince voters he is still up to the job, especially after recent video clips — some edited — rekindled concerns about his age. Donald Trump, 78, also faces questions about his age, mental acuity and temperament. Next month he will be sentenced for his criminal conviction in New York.

What happens if one of them suddenly drops out of the race — or dies? The succession battle could be messy.

How likely is this?

Not very, say betting markets. The two candidates remain heavy favourites to win the vote on November 5 — bettors place a nearly 87 per cent chance on a Biden or Trump victory, according to RealClearPolitics.

Both candidates are now beyond the average lifespan of US men.

But Trump’s biggest obstacles are his legal problems — both the small possibility that he’ll be sentenced next month to jail; and his colossal legal bills.

Meanwhile, conspiracy theorists and Trump supporters have speculated for months that Biden would be forced from the race, to be replaced by either Michelle Obama; California governor Gavin Newsom; or some other Democrat.

Voter anxieties about Biden’s age have also prompted some Democratic commentators to question whether he should be replaced on the ticket. That debate peaked in February after special counsel Robert Hur’s report on Biden’s handling of classified documents, which described him as a “an elderly man with a poor memory”.

But both parties appear set on fighting for the White House with two unpopular candidates. Neither candidate has remotely indicated that they would quit the race voluntarily.

What if Trump or Biden drops out or dies before the conventions?

Both candidates easily won their party’s primary vote earlier this year. If they dropped out now, it would be up to delegates at the forthcoming Republican and Democratic conventions to find replacements.

That would make July’s Republican convention in Milwaukee or the Democratic convention in Chicago in August akin to conventions decades ago, when candidates canvassed each state’s delegation for floor votes.

State delegates would be “uncommitted” — no longer beholden to their state’s primary result — and able to vote for any candidate they liked, said Elaine Kamarck at the Brookings Institution think-tank. It might take several rounds of voting to find a nominee.

“Presumably, for Democrats, they would pick [vice-president] Kamala Harris,” said Derek Muller, professor at the University of Notre Dame’s law school.

But Harris’s approval rating is just 39.4, according to FiveThirtyEight — even lower than Biden’s 39.9 per cent. Other Democrats would almost certainly jump into the race.

Trump hasn’t yet announced his pick to be his running mate. So the Republican convention would be a “little bit more of a freewheeling world”, Muller added.

Neither party’s rules say that the running mate must succeed a presidential nominee who quits or dies.

The whole replacement process would “look messy” with “a lot of bargaining, a lot of trading favours, a lot of speeches to state delegations at conventions”, said Kamarck.

Has a presidential candidate dropped out before?

Yes, but when party primary rules were different.

Lyndon Johnson, the sitting Democratic president in 1968, shocked the nation that March by pulling out of the race, saying the presidency must not be sullied by “partisan divisions” while he focused on the contentious Vietnam war.

Robert F Kennedy, who hoped to be the nominee, was assassinated that June, leaving Hubert Humphrey to win the party’s backing at a Chicago convention marred by protests over the war. Democrats are bracing for anti-war protests — this time over Gaza — at their convention this year, again in Chicago.

Four years after LBJ’s shock withdrawal, Democrat Thomas Eagleton dropped out as the running mate of the party’s presidential nominee George McGovern. The full Democratic National Committee took control of the replacement process — setting a precedent.

These days, if either candidate is gone before the convention, the party leadership — the DNC or Republican National Committee — would step in to manage the fallout.

“The simple thing to remember is: the parties are in control up until election day,” said Kamarck.

What would happen if a candidate dropped out after the conventions?

The party committees would decide a new nominee by vote. But first there could be an almighty succession battle.

For the Democrats, vice-president Harris would start as favourite, despite her own dismal approval numbers. But California governor Newsom would be a contender to replace Biden. Michigan governor Gretchen Whitmer and Illinois governor JB Pritzker are other possible runners. The problem for all of them is that they lack national name recognition, and are considered more plausible candidates for 2028.

The Republican fallout if Trump were incapacitated could be chaotic. During the primary, Republicans like Florida governor Ron DeSantis and entrepreneur Vivek Ramaswamy tried to capture Trump’s Maga supporters, and might fancy their chances. But Trump’s closest primary rival, his former US ambassador to the UN Nikki Haley, came from the more traditional conservative wing of the Republican party. So the battle to replace Trump would be an ideological fight too.

When would it get even more messy?

If either man dropped out after winning the election on November 5, but before the Electoral College voted to formally make him president-elect, things could get weird.

The electors in the Electoral College “wouldn’t be beholden to anybody”, said Kamarck. “As a matter of practical politics, they probably pick the vice-presidential nominee . . . but that’s a little ambiguous.”

Once the Electoral College has voted, it would be more straightforward: the US constitution’s 20th amendment says that if the president-elect dies, the vice-president-elect succeeds them.

Once inaugurated, that new president could nominate a vice-president under the 25th amendment. That choice would then have to be approved by a majority of both chambers of Congress.

Additional reporting by Oliver Roeder in New York