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At many points during 2020, people have turned their eyes skyward and asked, “What next?” Fate having been tempted, the news comes this morning that President Donald Trump has tested positive for the coronavirus just a month before Election Day, and while voting in many states is already under way. Although there is no indication yet that he has a severe case of COVID-19, the question of how the electoral process handles a candidate’s serious illness or death is now newly relevant.

There is no real possibility of delaying the election. That would require legislation—the House, the Senate, and the president agreeing quickly on new dates—which is politically unlikely, and would be legally awkward when voting has already started. Instead of postponing or redoing the election, the system relies instead on replacing candidates. The rules for doing so are clear, but what will happen under those rules is anything but.

Both parties provide in their rules for replacing a candidate. Even at this late date, if a candidate died or became so sick that withdrawing was necessary, party leaders would confer and select a replacement. The process by which they would do this is not set, and is entirely up to them. The leadership in this case are the 168 members of the Republican National Committee, and the 400-plus members of the Democratic National Committee. (The RNC allows for the possibility of reconvening its national convention, but doing so this late seems unlikely.)

The obvious replacement for a presidential candidate who dies or drops out is the person’s running mate—who, after all, is running for the post of presidential understudy. But neither party would be formally bound to move the vice-presidential nominee up to the top of the ticket. With the stakes as high as they are, no one should be surprised if other candidates were to make a play for the top spot. And if the running mate were to be chosen, the party would need to pick a new vice-presidential nominee—a process that would necessarily be wide open. Drama would surely ensue.

It is too late to reprint ballots at this point. Not only have millions of people voted already, but the process of printing and distributing ballots is simply too time-consuming to try to squeeze it in before November 3. The law recognizes that at a certain point, the ballots say what they say, even if what they say is no longer accurate. As a political matter, it would be crucial for the party replacing its candidate to broadcast its choice to the public with speed and clarity, so that people would know as clearly as possible whom they were voting for (or against), even if that’s not literally who is on the ballot. If people have already voted but want to change their mind, in some states they would be allowed to spoil their ballot and cast a fresh one, but this would add stress to a system that is already beleaguered this year. Some voters would be stuck, casting a vote for one candidate that ends up getting counted for another. This would put pressure on the party to choose the vice-presidential nominee to move to the top of the ticket—if early voters cannot change their vote for president, at least their vote would go to the person they had simultaneously voted for to be the presidential candidate’s understudy.

Perhaps more important, the party would need to coordinate its Electoral College designees—the people who cast the actual electoral votes when the party’s candidate wins a state. If a presidential candidate dies or drops out before the day the Electoral College casts its votes (this year, December 14) the party would coordinate its electors to vote for a chosen replacement. Again, the process by which they would do so is up to them.

No such process was in place in 1872, when the Democratic presidential candidate, Horace Greeley, died between Election Day and Electoral College day. The confused electors scattered their votes among various candidates. A few voted for Greeley anyway, but Congress refused to count those votes. Because Greeley had lost the election, it did not matter much, but it did set a precedent that the electoral votes for someone who is already dead do not count. Learning from this debacle, the Republican Party was prepared when Vice President James Sherman died a few days before Election Day in 1912. Sherman and his running mate, President William Howard Taft, got trounced in the election, so the stakes for the electors were again low. This time, the party was able to guide its electors all to cast their votes for the then-president of Columbia University, Nicholas Butler.

As the inauguration grows closer, things do get clearer. If a winning candidate dies after the Electoral College votes, the Twentieth Amendment would kick in. Section 3 of the amendment provides that if the president-elect dies, the vice president–elect swears in as president in his stead on January 20. If both the president-elect and vice president–elect die, the Presidential Succession Act of 1947 dictates that the Speaker of the House would resign from the House, swear in as acting president, and serve out the term.

As messy as all of this could be, even messier are the possibilities if a candidate becomes very sick before the election, but does not die. What if he—unwilling to give up on the possibility of recovering—does not withdraw? The party would be stuck. Some might attempt to interpret the party rules to allow the ouster of such a candidate (the RNC rules, in particular, use language that offers some wiggle room), but no party would want to stage that fight in the middle of an election. If the party leaders could not persuade the candidate to drop out, he would be left in place to hobble across the finish line as best he could.

There is a final, additional dimension to these possibilities, given that one of the candidates—the one with the virus—is currently the president. The Twenty-Fifth Amendment provides for an incapacitated president to transfer power to the vice president temporarily, until he recovers. Section 3 allows the president to choose to do this; Section 4 provides for the vice president and the Cabinet to do it without his consent. What if the president invoked Section 3 but, expecting to recover, wanted to remain as a candidate? Or what if the vice president and the Cabinet invoked Section 4 and the president contested it, sending the case to Congress for a resolution, as Section 4 provides? The party rules are separate from this process, and thus there is nothing legally binding that would prevent a president who has lost his powers from remaining on the ballot. Even if Section 4 were invoked and the president lost the congressional vote, the Twenty-Fifth Amendment is based on the notion that the president might recover—he is allowed to keep trying to retake his powers. As such, it would be hard to use this as a basis to replace him as a candidate, though someone could try.

In the end, we have pretty good processes in place for handling a presidential candidate’s serious illness or death at various stages of the process. That does not mean, though, that these processes wouldn’t be accompanied by serious political upheaval. We know who the decision makers would be, in other words, but we have no idea what they would decide—and what voters’ reactions would be. If President Trump’s condition worsens, hang on to your hats.

This story is part of the project “The Battle for the Constitution,” in partnership with the National Constitution Center.

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