As the nation is trying to get through the coronavirus pandemic, America is also trying to get through a presidential election.

The crisis has already affected the election in tangible ways, with states pushing back their primary contests and all remaining campaigns putting a hiatus on in-person campaign rallies. Furthermore, President Donald Trump and the two remaining contenders for the Democratic nomination — former Vice President Joe Biden and Sen. Bernie Sanders — are all in their 70s and at higher risk for more severe Covid-19 symptoms.

Biden is working and social distancing at his home in Delaware, where he’s been holding press conferences and virtual campaign events from his recreation room. Trump and Sanders, who have each been working in the White House and Senate, could be more at risk simply because they’re coming into contact with more people each day.

To be clear, recovery is possible at any age, and thus far, all three men appear to be healthy. But what if they weren’t?

Many are wondering what would happen if the presumptive nominee of either party got sick with Covid-19, the disease caused by the novel coronavirus, and became physically unable to accept the nomination before the party’s conventions this summer. Or, more worrisome, what would happen if a party nominee were to die before the general election?

“There’s not a lot of precedent to draw on; in fact, there’s none in which you’ve had an incapacitated nominee,” said Rutgers political science professor Ross Baker. “We elect mortals to the presidency. They suffer from all the ills that befall mortals.”

Presidents have died shortly after taking office (William Henry Harrison died six weeks after assuming the presidency in 1841, and Franklin Delano Roosevelt died a few months into his fourth term). But a death before a candidate accepts the nomination or gets inaugurated is uncharted territory in American politics.

“It’s kind of miraculous it never happened,” said Julia Azari, a political science professor at Marquette University who studies political parties.

A lot would depend on when in the nomination process a candidate became ill, experts say. For instance, if a presumptive nominee died before the respective party convention took place, a party — through its delegates — can select a new one. But if a death or vacancy occurred after a convention, party leaders would play an even bigger role in deciding the replacement.

“In the highly unfortunate event that any person in that situation passed away, people would understand that contingencies would need to come into play,” Azari said.

Here’s what we know about how the nomination process could change if either the Democratic or Republican nominee got Covid-19.

What happens if the nomination process isn’t completed

There are multiple scenarios around how a new presidential nominee could be selected in the case of severe illness or even death. It depends on how far along in the nomination process we are, according to New York University law professor Rick Pildes, an expert on constitutional and electoral law.

Here are how the different scenarios could play out:

A presumptive nominee or nominee is sick but not dying: Pildes pointed out that a nominee does not have to be physically present in order to accept a nomination. So considering our current situation with coronavirus, if either Trump or Biden were hospitalized with a non-life-threatening case of coronavirus, they could accept the nomination in writing or with a phone call.

Pildes pointed out that a nominee does not have to be physically present in order to accept a nomination. So considering our current situation with coronavirus, if either Trump or Biden were hospitalized with a non-life-threatening case of coronavirus, they could accept the nomination in writing or with a phone call. A presumptive nominee or nominee is sick but their prognosis is unclear: If the timing of a nominee getting sick lined up around the convention, it’s worth remembering delegates are not legally bound to a particular candidate. Delegates theoretically could switch to a different candidate during the convention for any reason, Azari said. However, the advice of party leadership would also likely play a role in how delegates act in such a scenario.

If the timing of a nominee getting sick lined up around the convention, it’s worth remembering delegates are not legally bound to a particular candidate. Delegates theoretically could switch to a different candidate during the convention for any reason, Azari said. However, the advice of party leadership would also likely play a role in how delegates act in such a scenario. A presumptive nominee dies before the convention: If the person who has a clear majority of delegates dies before the party’s convention, delegates at that convention can then go about debating and selecting an alternate nominee. Again, delegates aren’t legally bound to a particular candidate.

“That scenario is straightforward at least in principle,” Pildes said. “If the candidate who has won a majority of the delegates or who clearly would be the presumptive nominee were to die before the convention, then the convention could select another candidate as the nominee.”

What happens after the convention takes place

If a nominee were to die or otherwise become incapacitated after the party’s convention, the nomination process becomes less straightforward. But essentially, the party would still step in and decide.

It’s nearly impossible to call back all the delegates for another convention, Pildes said. “You can’t reconstitute the convention, that’s just too unwieldy. At least to the Democratic Party, the rules specify the DNC in a circumstance like that would choose the replacement nominee for the party.”

So the number of people making the decision would be much smaller, reduced from thousands of delegates to about 447 DNC members, which are composed of state-elected members, current and former party officials (presidents, members of Congress, etc.), and representatives from party committees.

Here’s what the Democratic Party’s rules and bylaws say about the process:

Filling a Vacancy on the National Ticket: In the event of death, resignation or disability of a nominee of the Party for President or Vice President after the adjournment of the National Convention, the National Chairperson of the Democratic National Committee shall confer with the Democratic leadership of the United States Congress and the Democratic Governors Association and shall report to the Democratic National Committee, which is authorized to fill the vacancy or vacancies.

For Democrats in 2020, that would mean DNC Chair Tom Perez would confer with House Speaker Nancy Pelosi, Senate Minority Leader Chuck Schumer, and New Jersey Gov. Phil Murphy (the current chair of the Democratic Governors Association) and then issue a report to the full 447-member DNC. The party as a whole would then meet, deliberate, and pick a new nominee.

If a nominee had already selected a vice presidential pick, that could certainly factor into the party’s decision if the nominee dies. But Pildes noted it would not automatically mean the vice presidential pick would become the nominee.

For Republicans in 2020, the answers are a little more straightforward because Trump is the incumbent and has an automatic No. 2 in Vice President Mike Pence. Were Trump to die in office before his term was up, there’s a straightforward constitutional mechanism in place (Article 20 of the Constitution) for Pence to assume those duties.

In a sense, this scenario would be a return to how nominees were chosen before the 1970s — by the parties. While candidates competed in primaries in the 1950s and 1960s, they did that so state and national party leaders could then decide who was best for the presidency.

After a raucous 1968 Democratic National Convention in Chicago, the system switched in the 1970s, giving voters — not parties — the power to decide. Conventions used to be the setting where the nomination was actually hashed out, whereas now, the majority of delegates are awarded before the convention even takes place.

Either party could face a legitimacy crisis if voters were not willing to accept party leaders once again playing such a decisive role in selecting the nominee, said Azari. The 2016 Democratic primary saw a lot of Sanders supporters mistrusting the system after emails leaked seeming to show DNC officials favoring Hillary Clinton. But given how unprecedented it would be for a nominee to get seriously sick or die in the middle of an election year, Azari said she thinks most voters would be looking for leadership from institutions.

“Most people would be reasonable,” she said. “We are all drawn to chaotic scenarios, but I think some gravity and general concern for the process would weigh out in this situation.”

The rest of the primary calendar is more uncertain due to the coronavirus

At the moment, the nomination looks like it’s headed to a pretty clear conclusion. Joe Biden has more than 1,100 delegates and needs 1,991 to win the nomination. While Sanders has shown no signs of dropping out, Biden seems well on his way to being the presumptive nominee.

But we also don’t know when exactly he is going to hit that threshold, because some states are postponing their elections due to the coronavirus outbreak. More than a dozen states and territories have pushed back their primary elections or moved to only mail-in voting to protect poll workers and voters. We don’t know yet what these delays will mean for the nominating process.

In the meantime, the Democratic National Committee is urging states to get their voting systems to be more resilient during a public health crisis. That means states are beefing up vote-by-mail systems to be more accommodating, protecting both voters and poll workers in the process.

“In order to ensure the voices of voters are heard, the DNC is urging the remaining primary states to use a variety of other critical mechanisms that will make voting easier and safer for voters and election officials alike,” DNC Chair Tom Perez said in a recent statement. “The simplest tool is vote by mail, which is already in use in a number of states and should be made available to all registered voters.”

In some states, like Wisconsin, the DNC is teaming up with the state party to sue to expand access to vote by mail and to easier forms of voting registration. And two Democratic senators have secured funding in the latest Senate coronavirus package to increase America’s vote-by-mail capacity.

If adopted on a more widespread basis, vote-by-mail could help Democrats decide their nominee while still following public health experts’ social distancing guidelines. But if states keep delaying their primaries and Sanders continues to stay in the race, it could allow more uncertainty about who will be the nominee.

That uncertainty would only increase if the presumptive nominee tested positive for the coronavirus.