But in response to questions from journalists over the last few weeks, the embattled Democratic president has given some clues as to what could make him step aside — especially as the calls from his own party to end his candidacy continue unabated.

Here are the things Biden has cited — some serious, others not — that would make him reconsider his run:

Divine intervention

It was a defiant answer that indicated Biden had no intention whatsoever of dropping out.

During an ABC News interview that marked the first major test of his fitness for office, anchor George Stephanopoulos asked the 81-year-old Biden whether he had convinced himself that only he could defeat his Republican opponent, Donald Trump.

“I have convinced myself of two things,” Biden said. “I’m the most qualified person to beat him, and I know how to get things done.”

Stephanopoulos pressed a little further: “If you can be convinced that you cannot defeat Donald Trump, will you stand down?”

“It depends,” Biden responded. “I mean, if the Lord Almighty comes out and tells me that, I might do that.”

Cold, hard data

No politician ever wants to lose — and it seems Biden would be willing to exit if he had numerical proof that that’s what would happen.

In a news conference at the close of the NATO summit in Washington last week, Biden was asked whether he would step aside if aides showed him that Vice President Kamala Harris would be a stronger opponent than he would be against Trump.

Biden’s initial response was “no,” but then he elaborated.

“Unless they came back and said, ‘there’s no way you can win.’ Me,” he said. “No one is saying that. No poll says that.”

The limited polling available suggests a competitive race with several months before the election. Several polls of voters give Trump a slight advantage, while others show neither candidate with an advantage.

A fateful accident

Biden wasn’t directly asked the hypothetical, but he threw in a new scenario anyway.

As Speedy Morman, a host on the entertainment network Complex, was wrapping up his interview with Biden last week in Detroit, he had one more closing question for the president: “We will 1,000 percent — in your words — see you on the ballot this November?”

Quipped Biden: “Unless I get hit by a train, yeah.”

Morman responded: “Let’s hope that doesn’t happen, for your safety’s concern.”

A not-yet-diagnosed medical ailment

Biden spoke with BET journalist Ed Gordon for an interview set to air Wednesday night. During the conversation, Gordon asked Biden if there were any factors that would make him reevaluate his candidacy.

He didn’t repeat the other reasons that he had previously listed — but rather surfaced a new one.

“If I had some medical condition that emerged,” Biden told Gordon. “If doctors came to me and said, ‘you got this problem, that problem.’”

The health of Biden, the oldest person to be U.S. president, has been scrutinized well before his catastrophic debate performance.

After his latest physical in February, presidential doctor Kevin O’Connor said Biden “remains fit to successfully execute the duties of the presidency.” A neurological exam, taken more than a month prior, showed no signs of a stroke, multiple sclerosis or Parkinson’s disease, according to O’Connor. The physician also said a cognitive exam was unnecessary.

Biden tested positive for COVID-19 Wednesday while trying to shore up support among disenchanted voters key to his reelection chances. The diagnosis prompted him to cancel a meeting with members of a Latino civil rights organization in the battleground state of Nevada.