President Biden's lackluster debate performance Thursday night, marked by a raspy voice, gaping facial expressions, rambling answers on key questions and a perceived failure to refute several lies from former President Donald Trump, has fueled concern among many Democrats in Washington and sparked some discussion about whether there's a way to replace him on the Democratic ticket in the 2024 presidential election. 

Biden campaign spokesperson Mia Ehrenberg, asked if the president would step aside after his debate performance, replied, "Absolutely not." Asked if there are conversations about Mr. Biden stepping aside, campaign spokesman Michael Tyler said, "There are no conversations about that whatsoever."

And a newly re-energized Mr. Biden showed no sign of backing away when he spoke at a campaign rally in North Carolina the following day. "I don't debate as well as I used to," he acknowledged, but added, "I know how to get things done. And I know, like millions of Americans know, when you get knocked down, you get back up."

Whether the 81-year-old presumptive Democratic nominee should be replaced is a question for Democrats. How that process would work in accordance with Democratic National Committee rules is another. 

Here's what the process could look like, according to experts and DNC rules. 

Biden would have to step aside voluntarily 

The president couldn't be forced to step down from the race, election law and process experts agree. It's something he would have to do voluntarily. Mr. Biden possesses nearly all of the delegates from the primary process and most states have already completed their primaries.

"This is all premised on Biden himself agreeing to do this," said John Fortier, a senior fellow at the American Enterprise Institute who studies the Electoral College process and continuity of government. 

Replacing a party nominee like Mr. Biden is "really hard and unlikely to happen," Fortier said. 

"I don't think it's going to happen because there are all sorts of reasons why it's difficult," he said. 

The timing of any replacement of a major party's nominee 

If Mr. Biden were to step aside, that would almost certainly happen "before or during the convention," Fortier said. 

Stepping aside before the Democratic convention is legally easy but politically difficult, said Derek Muller, a law professor at the University of Notre Dame who specializes in election law. 

"It's politically messy before the convention but it's not legally messy," Muller said. There is no legal impediment to his stepping aside as the presumptive Democratic nominee.

Biden would likely have significant influence on his successor if he were to step aside before the convention

If Mr. Biden were to step aside before the convention, which begins on Aug. 19 in Chicago, he would likely have significant influence on the Democratic Party's choice of who would take his place on the ticket. The most likely candidate would be Vice President Kamala Harris, Muller and Fortier agree. 

"He could negotiate of course beforehand with people to try to get a common front," Fortier said. "By far the most likely outcome is that it would go to Kamala Harris."

Delegates are loyal party people, and Fortier said he suspects they "would be able to rally the troops" around one candidate. 

"I think Harris would be the default option because she is the vice president and is the presumptive vice presidential nominee," Muller said. 

If Harris were to become the presidential nominee before the convention, she would be able to pick her VP replacement, perhaps another big-name Democrat who performed well in an open convention. 

But it wouldn't have to be Harris.

A contested convention?

At this point, the Democratic National Committee is expected to hold a virtual roll call about a week and a half before the convention, on Aug. 7, to formally nominate Mr. Biden and Harris, in order to meet a ballot certification deadline in Ohio on that date.

The convention is scheduled to begin Aug. 19 in Chicago, but an Ohio law requires that presidential candidates formally be nominated 90 days before Election Day. 

Because of the virtual roll call, "I don't know what that looks like in the event that there's going to be a contested convention," Muller said. 

If Mr. Biden did step aside and Democrats were unclear on who the nominee should be, they could decide to jettison the virtual roll call and cede Ohio to Trump, in order to give candidates a little longer to prepare their pitches for the convention.

DNC rules say delegates "elected to the national convention pledged to a presidential candidate shall in all good conscience reflect the sentiments of those who elected them."

Fortier says this means delegates must vote for Mr. Biden on the first ballot. 

"The delegates are bound on the first vote, and Biden would essentially decline or release them, and then we move onto the second round where everybody is uncommitted," he said, if Mr. Biden steps aside. 

Muller said there could be some room for interpretation, and if Democrats were to coalesce around a new candidate ahead of the convention, they might be able to vote for someone other than Mr. Biden. 

"I think there would be a strong incentive for people to not vote for Mr. Biden, but to show strength for some other candidate."

If a first ballot is inconclusive, so-called superdelegates — party leaders and elected officials in the party — could vote in subsequent ballots. And delegates would continue to vote until a nominee is secured. That could be a lengthy process, depending on how united or divided delegates are. 

If Democrats don't throw their support to one candidate, it could get messy. 

Past convention fights

Convention fights can be long and grueling. The 1924 Democratic National Convention took a record 103 ballots to nominate presidential nominee John W. Davis and vice presidential nominee Charles W. Bryan, who went on to lose in November. 

In 1968, Robert Kennedy — father of current independent candidate Robert F. Kennedy Jr. — jumped in the race late, after President Lyndon Johnson announced in late March he wouldn't seek reelection. Kennedy was on track to win more delegates than anti-war candidate Sen. Eugene McCarthy when he was gunned down just after his speech following his victory in the California primary. 

Instead of nominating an existing candidate, the Democratic Party chose then-Vice President Hubert Humphrey, Johnson's pick, at the convention in Chicago. Humphrey lost that November to Richard Nixon. 

If Democrats held a contested convention today, presidential hopefuls would go and make their pitch to the state delegations. 

But again, Fortier said replacing the top of the ticket is "really hard and unlikely to happen." 

In:
• Joe Biden
• Democratic Party
• 2024 Elections

Kathryn Watson is a politics reporter for CBS News Digital, based in Washington, D.C.