After the first debate between US President Joe Biden and his presumptive challenger Donald Trump last Thursday night, it's no exaggeration to say that the liberal-leaning part of the country was in despair.

Again and again throughout the night, Biden sounded frail and delivered sentences that made no sense. Social media users joked that Vice President Kamala Harris should be "subbed in" during commercial breaks, and that the debate resembled a humiliating family fight.

Since then, Biden has blamed his performance on exhaustion from extensive international travel before the debate, and a little bit of calm has settled in.

"Where the time right after the debate saw a lot of nervous energy run through the party, the last couple of days have been a shoring up of the Democratic basis," Cathryn Clüver Ashbrook, a German-American trans-Atlantic politics expert with the German Bertelsmann Foundation, told DW.

"And would-be candidates that were floated to replace Joe Biden immediately after the debate have come out very strongly in support of the president."

California's Democratic governor, Gavin Newsom, who was among those being suggested as a replacement, said on US broadcaster MSNBC, "You don’t turn your back [on your candidate] because of one performance. What kind of party does that?"

Not everyone in the Democratic Party sees it the same way. Lloyd Doggett, a member of the US House of Representatives from Texas, became the first sitting Democrat in Congress to call for Biden to step back on Tuesday.

"Recognizing that, unlike Trump, President Biden's first commitment has always been to our country, not himself, I am hopeful that he will make the painful and difficult decision to withdraw," Doggett was quoted by The Associated Press news agency. "I respectfully call on him to do so."

How likely is Biden to step down?

Doggett is not a major player, but concerns about Biden's age have only gotten stronger since the debate last Thursday.

Switching out a candidate, especially a sitting president, this late in the race would be highly unusual. But it's not impossible.

"To replace a candidate at this point, ideally, he would step back himself," said Filippo Trevisan, an associate professor at American University's School of Communication in Washington. "That would be simplest."

Trevisan also said, though, that he does not see Biden, who has been in national politics all of his adult life, giving up on the chance to win a second term in the White House.

"Things could change over the next week when they look at poll numbers," said Trevisan, a US politics and campaign expert. "But right now, based on what we've heard from [Biden] and his campaign team, I think it's highly unlikely he'd step down."

On Monday, the Biden campaign released an ad showing a forceful Biden talking to a crowd, saying, "I know I'm not a young man, but I know how to do this job… and I know like millions of Americans know, when you get knocked down, you get back up."

What would happen if Biden did step down?

In the primaries, supporters of the Democrats and Republicans cast ballots for who they want to be their candidate. Whoever wins in each of the 50 states receives the support of that state's delegates. At the Democratic National Convention in August, these delegates will vote on who will be the Democrat's presidential candidate. The vast majority of them are pledged to Biden. They are not legally required to vote for him, but by virtue of how the US primary process works, it's what is expected of them.

If Biden steps down, "it's a free-for-all," said Trevisan. "They could vote for whomever they want."

That's what is called an open convention, and delegates would vote according to their conscience. Democratic Party leadership would pick a candidate that they think has the best chance of winning the presidential election, and then try to get delegates to back him or her.

"I would say Harris really has the right of first refusal.," J. Miles Coleman, an election analyst with the University of Virginia Center for Politics, told DW right after the debate.

But Trevisan said picking Harris in such a case might not actually be the best move.

"Her association with the Biden presidency could be a negative," he said. "Her approval numbers are similar to Biden's."

When a president becomes incapacitated while in office, for example, through a medical emergency, the vice president takes on the job. But Harris would not automatically become the candidate if the president were to step down ahead of the convention.

Possible Biden replacements: Harris, Newsom, Whitmer

A number of names have been floated, particularly in the days after the debate, for who could become the presidential candidate if Biden was out of the picture. In addition to Vice President Harris and California's Governor Newsom, there is also Governor Gretchen Whitmer of Michigan.

Whitmer was first elected governor in 2018 and reelected in 2022. Her reelection was considered a big success ― 2022 was a midterm election under a Democratic president (Biden), and it's usually harder for candidates from the incumbent's party to win over voters. But Whitmer managed to win another term with a larger-than-expected margin and in the important battleground state of Michigan, which is not considered a sure-fire win state for Democrats like California or New York.

But just like other powerful Democrats, Whitmer has publicly supported Biden after the debate, writing on social media platform X that "we need to reelect Joe Biden and Kamala Harris."

Nancy Pelosi of California, who was speaker of the House for two terms and is somewhat of a grande dame in the Democratic Party, has called on both Biden and Trump to undergo tests for their health and mental acuity. But according to AP, she also emphasized that Biden is on "top of his game, in terms of knowing the issues and what is at stake."

Could another candidate be elected against Biden's will?

What if Biden doesn't step down, but Democrats still want to install another candidate at the convention in August?

"That's not going to work unless the Democratic Party statutes are overruled or changed," said Clüver Ashbrook of the Bertelsmann Foundation. The US, after all, "have had primaries where Joe Biden has claimed 99% of the delegates. To willingly go against a delegate vote, that circumvents a democratic process. When the country is in a perilous moment in its own democracy, nobody is going to attempt that in the Democratic Party."

If Biden were to drop out even later — after the convention, for instance, over health reasons — not even the delegates could vote on a candidate. Instead, the Democratic National Committee would convene and decide on a candidate ― something that would certainly fuel discussions on the state of US democracy.

Edited by: Andreas Illmer