Joe Biden is 80 and not very popular. Donald Trump is 77, not very popular, and facing four indictments. The possibility that one or both parties might replace either man before they secured their respective presidential nomination—or afterward—because of health, death, or legal conviction is worth considering if only because weird stuff happens all the time in American politics. Twenty-three years ago, Americans had to take a crash course in Florida election law, such as what distinguished hanging chads in Broward County versus butterfly ballots in Leon County, as the 2000 presidential contest and its knife’s-edge vote tally in the Sunshine State consumed the nation. In 2024, a visit to the penitentiary or an onstage collapse could send us scrambling to the rule books. There are rules governing what to do if, say, Trump is in handcuffs or if Biden dies. The bad news is that there are enough uncharted waters ahead that we may feel like we’re in the Bermuda Triangle, and the compass is spinning like a whirlpool.

Let’s start with the health of each man and what it means. First, you might or might not be comfortable knowing that neither is likely to die before Election Day. According to data from the Centers for Disease Control, an 81-year-old non-Hispanic white male—as Biden will become this November—has a 6 percent chance of dying next year. (It speaks to the president’s age that about half of non-Hispanic white males in Biden’s birth cohort have already died.) On the upside, Biden seems to be physically active, and he has amazing medical care. Commanders in Chief are never more than a few yards from the best doctors, so Biden’s chances of keeling over, even as an octogenarian, are pretty low. Indeed, none have died of natural causes in office since Franklin Roosevelt, who had been in declining health, died 78 years ago.

Trump is only about four years younger than Biden and, by all appearances, in worse physical shape, but still, the actuarial tables suggest he will be with us for at least 14 more months.

Trump’s legal woes could conceivably deny him the GOP nomination. He is facing four separate indictments, alleging he falsified business records related to the hush money paid to Stormy Daniels, brought classified documents with him out of the White House, and attempted to overturn the elections in Georgia and Washington, D.C.

Are GOP voters or party elites concerned enough about Trump’s legal troubles to dump him? So far, it seems like no. He currently sits at a 56 percent polling average among Republicans, with his closest opponent, Florida Governor Ron DeSantis, at 15 percent.

If Trump is convicted after most of the primaries, but before the Republican convention, he’s still likely to top the ticket. According to the RNC rules, convention delegates are bound to follow their state’s voters in nominating a candidate, and conviction wouldn’t stop that, barring some sort of unlikely last-minute rule change. There are no laws in America, nor RNC rules, that forbid felons from running for president. Eugene V. Debs, the 1920 Socialist Party nominee—and its presidential standard-bearer in four prior elections—won nearly a million votes while in federal prison in, of all places, Fulton County, Georgia.

This is, of course, leaving aside the question of whether insurrectionists can be denied a spot on the federal ballot (in line with the 14th Amendment) and whether Trump is one—issues that will confront secretaries of state in the coming months.

“We’ve obviously never come close” to electing an incarcerated nominee, says Richard Pildes, Sudler Family Professor of Constitutional Law at New York University. “I would imagine that the president, because he would be the president at that point, would go to the courts and argue that he can’t fulfill his constitutional duties as the elected president of the United States if he’s in jail, and the sentence should be suspended and not put into execution until after he’s no longer president.” That’s the case for at least the state incarceration since, in a federal one, he may just be able to pardon himself.

So, if Trump wins the 2024 election while convicted or incarcerated, which is certainly possible, he could still serve as president.

The Next Six Months

Delegates at the Democratic convention in Chicago are already technically allowed to vote their conscience, so if Biden died or became severely ill before the convention, they would be free to vote for Kamala Harris or anyone else.

On the Republican side, where delegates are bound to vote the way their state does, a Trump-Is-Dead scenario is more complicated. Pildes says, “In this situation, you might easily imagine that the Republican National Committee would change the rule or find some way to interpret its rules to deal with the situation” and avoid nominating a dead person. They might nominate the second-place finisher in the primaries, or maybe they’d select Trump’s running mate if he had already named one, or perhaps they’d all gather in Milwaukee, the site of the 2024 RNC convention, to vote for a dead man before announcing a nationwide referendum followed by a second convention. There’s no way to know.

Post-Convention

The DNC and RNC rules spell out exactly what to do if a nominee dies or is incapacitated between the convention and the general election.

If it’s health, not death, then the unhealthy man or his caretakers would have to make the call since there’s no way to remove a nominee because party elites deem him unfit. Says Pildes, “I don’t believe the national party committees of the Republican or Democratic party have the legal authority to force a nominee out once the convention has selected that person as the party’s nominee.”

But if it’s death, then on the Democratic side it is the responsibility of the 447 voting members of the Democratic National Committee to fill a vacancy. And it’s up to Jaime Harrison, the party chair, when they meet and vote. A simple majority could select a nominee, which could be one of the party’s rising stars, like Michigan Governor Gretchen Whitmer, or it could just be President Harris, who would have been sworn in if Biden died or perhaps would have assumed powers under the 25th Amendment if he’s very ill.

The Republican process is different. The 168-member Republican National Committee (three from every state, Washington, D.C., and the territories) could reconvene the convention to fill the vacancy or just choose among themselves. If they did the latter, each state’s RNC delegation would vote, and those votes would be counted in the same proportions as their delegate counts (i.e., California would have more say than Alaska), or if a state’s RNC members can’t agree, their state’s proportion of the votes would be split up.

In and Around November

The course of action is unclear if a presidential nominee dies close to Election Day. According to Pildes, “Different states have different rules about how late in the [race] a party can replace its candidate on the ballot. And so, depending on when this event might happen, there could be some complexities about getting the ballot actually changed in various states.” An example from the Senate came in 2000 when Missouri Governor Mel Carnahan, a Democrat running for the US Senate, died in a plane crash, too late for his name to be taken off the ballot or for a new nominee to be selected. The late Carnahan won at the ballot box. The lieutenant governor who was sworn in as governor after Carnahan’s death appointed his widow as senator, and she served for almost two years until a special election.

In the presidential election, if the ballots aren’t changed in time, and a dead man wins, it’s unclear what the Electoral College can and would do. Presumably, the electors from states that voted for a dead man would vote for the winning vice-presidential candidate, but 33 states and D.C. require their electors to vote as they pledged, so the feasibility of that isn’t clear. It might require state legislatures to meet to change those elector-binding laws.

If death happened after the Electoral College had already met, it would be relatively straightforward: the 20th Amendment mandates that the vice president-elect take office.

But for right now, though Trump and Biden do not look strong, they do not look deathly weak either. Much to the annoyance of many voters, they are likely to continue their march to the nominations and face off again next year, culminating in the election and re-inauguration of one of two unpopular presidents, either of whom would be the oldest person ever inaugurated.

Though neither candidate is likely to die in the coming months, one may well be convicted of felonies and even sentenced, and the other is already the oldest president ever. It’s best to keep some contingencies in mind.