What happens if a presidential candidate dies before election day?

President Donald Trump's battle against the coronavirus appeared to intensify today as reports emerged that the US commander in chief was given oxygen before being hospitalized, with anonymous sources close to the White House warning that Trump has entered a critical stage in his treatment.

The scant reports coming out of Walter Reed Medical Center, where Trump was admitted Friday for treatment, are deepening questions among US officials, allies, and adversaries about the 74-year-old president's condition, and what might happen if Trump is rendered incapable of serving. 

To help answer those questions, Foreign Policy took a look at Trump's prospects for recovery, the potential paths of presidential succession, and what it means less than a month before a hotly contested election.

How serious is the president's condition?

As of Saturday afternoon, there are contradictory messages coming out of the White House, almost simultaneously. In a briefing to reporters on Saturday, White House physician Sean Conley said Trump was "doing very well" and improving from a mild cough and fatigue. But then immediately following the briefing, White House pool reporters released the following statement from "a source familiar with the president's health": "The president's vitals over the last 24 hours were very concerning and the next 48 hours will be critical in terms of his care. We're still not on a clear path to a full recovery." (Later reports suggested the anonymous source was White House chief of staff Mark Meadows.)

Trump has been given an experimental antibody treatment that is still undergoing clinical trials, and the vast majority of people with COVID-19 recover; overall fatality rates from the virus are just shy of 3 percent of confirmed cases in the United States. But he's still considered to be at a high risk, given his advanced age and obesity. 

The dueling messages led Trump himself to issue a Twitter missive downplaying worries about his health on Saturday afternoon: "Doctors, Nurses and ALL at the GREAT Walter Reed Medical Center, and others from likewise incredible institutions who have joined them, are AMAZING!!!" The president insisted he was "feeling well" and began firing off more tweets, urging for Congress to pass a stalled coronavirus stimulus measure.

How about Joe Biden?

Joe Biden, the Democratic presidential candidate and former vice president, announced Friday that he tested negative for the coronavirus, after sparring in close proximity to Trump in the first presidential debate this week shortly before the president announced his diagnosis. (Both were maskless.) Biden's running mate, California Sen. Kamala Harris, also announced she tested negative. But many health experts say that Biden will have to take more tests in the coming days to confirm the negative diagnosis after facing possible contagion from the president.

What happens if Trump takes a turn for the worse?

As legal experts and election observers have pointed out, it's important to understand election processes if a president becomes severely ill, incapacitated, or worse—without being too alarmist. The 25th Amendment to the Constitution allows the president to temporarily grant his powers to the vice president if he becomes incapacitated or too ill to properly do his job. Vice President Mike Pence, unlike other White House advisors, has tested negative for the virus. If the vice president were to somehow become incapacitated, the powers of the presidency would move to Speaker of the House Nancy Pelosi. In turn, the third in line to the presidency is the president pro tempore of the Senate, Iowa Republican Sen. Chuck Grassley, and the fourth in line is Secretary of State Mike Pompeo. 

But even though administration officials have insisted that the chain of command remains intact should the US military need to respond to a crisis, historically, the temporary incapacitation of the president has at least created optics issues for the White House. After the 1981 assassination attempt that hospitalized President Ronald Reagan, then-Secretary of State Alexander Haig insisted—wrongly—at a press briefing that he was temporarily in charge of the country. 

OK, but what happens if either candidate becomes incapacitated or dies before the election?

That's where things get complicated, even if it's an unlikely scenario, according to Joshua Tucker and Richard Pildes, both professors at New York University who have explored these questions in-depth for Washington Post's Monkey Cage blog. The constitution provides a road map, but not for every possible contingency. If a candidate wins the presidency, but then dies before assuming office in January, there's a straightforward answer, thanks to the 20th Amendment to the constitution: The vice president-elect (either Pence or Harris in this instance) would become president. 

If a candidate dies before the election, the national party committees would pick a new candidate for the top of each ticket. 

But we're a month away from the election, and some states have already started voting. 

That's where the already complicated becomes much more complicated, as Tucker and Pildes explain. Each state has deadlines for when candidates' names can be placed on the ballot; most have come and gone. And in many states, particularly in the wake of the pandemic, mail-in ballots have already been sent and voters are already mailing in their ballots. So at this point, even if Trump were to die or become incapacitated, there would be no practical way for the Republican National Committee to pick a new candidate, then have each state recast its ballots to reflect the new ticket. Those are uncharted waters, and it would take historic and complex legal battles to figure out how to proceed. 

So it could be up to the Electoral College?

Sort of. In some states, but not all, Electoral College delegates are required to cast a vote for the candidate that won the state's popular vote. Even in states without those binding laws, electoral delegates still follow the popular vote in practice. The problem comes if a winning candidate dies or becomes incapacitated: There is no precedent and little state legislation to address such a contingency. This points to more uncharted waters and more looming legal battles if that were to happen.

What if no candidate can secure a majority in the Electoral College?

Then, as in 1876, it would go to the House of Representatives to decide—but not on a straight vote as in normal House legislation. Instead, each state congressional delegation gets one vote for any of the top three electoral vote recipients in the election. In that long-shot scenario, that could give the Republicans a slight edge, since they control slightly more state delegations than do Democrats.

Staff writer Jack Detsch contributed to this report. 

Robbie Gramer is a diplomacy and national security reporter at Foreign Policy. Twitter: @RobbieGramer

Disclaimer: This article first appeared on foreignpolicy.com, and is published by special syndication arrangement.