“I don’t wear face masks like him,” Trump said of his opponent, former vice president Joe Biden. “Every time you see him, he’s got a mask. He could be speaking 200 feet away, and he shows up with the biggest mask I’ve ever seen.”

When moderator Chris Wallace asked Trump about the large rallies he’s been holding as a crucial component of his presidential campaign, the President joked that the only reason Biden didn’t do the same was because “nobody shows up to his events.” He would continue to have them, Trump said, and insisted that were safe. 

What a difference two days can make. 

Trump, his wife, Melania, and top aide Hope Hicks announced early Friday that they had tested positive for COVID-19 and were mildly symptomatic. The effects of the virus have been known to linger for much longer than the month left until the election. 

Now campaign staff, analysts, and operatives must scramble to figure out what a presidential campaign looks when one candidate is incapacitated, or at the very least, quarantined. Unfortunately, said Thomas Schwartz, distinguished professor of history and political science at Vanderbilt University, there isn’t much historical context to help them.

While Woodrow Wilson had a severe stroke while in office and left many of his duties to his wife, he wasn’t running for reelection. Ronald Reagan had cancer while in the White House but, again, was not campaigning. “You really have to stretch for comparisons here,” Schwartz said of the problem.

Dwight Eisenhower suffered a massive heart attack a year before winning his reelection campaign in 1956. His opponent, Adlai Stevenson, attempted to use the issue to argue that Eisenhower was too old to run; he was six years younger than Trump at the time.

Still, there have been times throughout American history, during the Civil War and World War II, for example, when sitting presidents were not around to campaign in-person. Front-porch style campaigning has been used by a number of candidates, namely Joe Biden. As long as the President’s symptoms remain mild, said Schwartz, he’ll likely participate in virtual rallies and interviews much like Biden has in the past. The debates could even continue through video.

But in-person rallies, debates, studio interviews, and Rose Garden announcements will be unlikely to resume for the duration of the campaign.

“This is terribly damaging to Republicans in general. Trump fed off of crowds and the absence of that can’t be helpful right now. It’s a damaging thing for his prospects,” said Schwartz.

If the President does bounce back quickly, however, he’ll be able to play to the argument of strength while eliciting sympathy. But if his illness is prolonged or worsens, his 2020 hopes will take a serious ding, Schwartz said. 

Meanwhile, his campaign will likely rely heavily on the use of surrogates in lieu of Trump: Vice President Mike Pence has tested negative for the virus and will likely be in front of cameras this weekend. If the President’s family members, Ivanka, Tiffany, Eric and Donald Jr., test negative they will also likely pick up some slack for the President, as will Lara Trump and senior advisor Kimberly Guilfoyle. 

There’s also little legal precedent about what would be done if the President were to succumb to his illness or become critically ill before November 3. “You can speculate to the moon on this,” said Schwartz. Many Americans have already cast their votes through early voting and vote by mail, further complicating the situation. Early voting begins next week in earnest across the country, and millions more will vote. 

Deceased candidates have won local elections before and have typically been replaced by another candidate of their party’s choosing, said Schwartz. “It would seem to me that a case could be made that people who had voted already voted for the Republican ticket, and the party could claim those votes.” Still, there would be a long legal challenge likely leading to the Supreme Court, he said. 

Trump’s Supreme Court Justice nominee Amy Coney Barrett said Friday that she had COVID-19 earlier in the year but has since made a full recovery.