President Joe Biden's performance in the first debate Thursday has sparked a new round of criticism from Democrats, as well as public and private musing about whether he should remain at the top of the ticket.
"There is a sense of shock at how he came out at the beginning of this debate. How his voice sounded. He seemed a little disoriented," David Axelrod, who served as a top White House and campaign official for former President Barack Obama, said on CNN.
"There are going to be discussions about whether he should continue," Axelrod added.
One Democratic lawmaker, asked by NBC News whether the debate inspired confidence in Biden, replied: "The best thing I can do to help Joe Biden is to pretend I didn’t get your text."
Publicly, Democratic officials continue to largely rally around Biden, and argue a lackluster performance doesn’t change the fundamental stakes of the election.
California Gov. Gavin Newsom, whose name is often floated as a potential alternative nominee, told reporters in the "spin room" after the debate that his party "could not be more wholly unified behind Biden" and said the president should not step aside.
But the private whispers whipped up after Thursday’s debate performance, during which Biden had a raspy voice, spoke softly and a times seemed to lose his train of thought, leading his aides to try to deflect mid-way through the debate by saying he had a cold.
Decision 2024
In the modern era, a national party has never attempted to adversarially replace their nominee, in part, because they know it would likely fail. The issue came before both parties in 2016, but neither took action.
Party rules make it almost impossible to replace a nominee without their consent, let alone smoothly replace them with someone else. And doing so would amount to party insiders overturning the results of primaries when Democratic voters overwhelmingly to nominate Biden. He won almost 99% of all delegates.
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And at the moment, there is no known, serious effort to push Biden off the top of the ticket.
Still, the Democratic National Committee's charter does make some provisions in case the party’s nominee is incapacitated or opts to step aside, and an anti-Biden coup at the convention is theoretically possible, if highly unlikely. So how would it work?
What happens if Biden drops out before the convention?
The only plausible scenario for Democrats to get a new nominee would be for Biden to decide to withdraw, something he's sworn off repeatedly during other bumpy stretches of his campaign.
He could do so while serving out the remainder of his term in the White House, as Lyndon Johnson did in 1968.
If Biden were to drop out between now and when he's scheduled to be formally nominated in August, it would create a free-for-all among Democrats since there is no mechanism for him or anyone else to anoint a chosen successor.
It takes a majority of the roughly 4,000 pledged delegates to win the party’s nomination. Biden’s won 3,900 of them. Under recent reforms, the party’s more than 700 superdelegates — Democratic lawmakers and dignitaries — are allowed to vote only if no one wins a majority of pledged delegates on the first ballot, so their votes could be crucial in a contested convention.
Since Biden's opponents all won effectively no delegates throughout the Democratic nominating process, there'd be a virtual clean slate heading into the convention, and the decision would likely come down to the convention delegates who were initially pledged to Biden.
Biden would have some influence over his pledged delegates, but ultimately, they can vote as they please so candidates would likely campaign aggressively to win over each individual delegate.
However, there's a potentially important wrinkle: Democrats plan to formally nominate Biden virtually ahead of the late-August convention to sidestep any potential concerns about ballot access in Ohio, where a technical quirk has complicated things
Democrats decided to plan a virtual nomination for Biden after Ohio Republicans balked at passing pro-forma legislation that would allow Biden to be on the ballot, even though the convention falls after a state deadline. But while Republicans passed a law to shift the deadline, Democrats decided to move forward with a virtual nomination nonetheless.
Could Democrats replace Biden against his will?
There’s no evidence the party would entertain a change without Biden’s consent. But even if they did, there is no mechanism for the national party to replace a candidate before the convention and certainly no way for them to anoint a chosen successor.
If large swaths of the Democratic Party lost faith in Biden, delegates to the national convention could theoretically defect en masse. Of course, they were chosen to be delegates because of their loyalty to Biden and have pledged to support him at the convention.
But, unlike many Republican delegates, Democratic delegates are not technically bound to their candidate. DNC rules allow delegates to “in all good conscience reflect the sentiments of those who elected them,” providing some wiggle room.
The party’s charter does contain provisions to replace the nominee in the event of a vacancy. The measure is intended to be used in case of death, resignation or incapacitation, not to replace someone who has no desire to step down.
That was the measure that then-interim DNC Chair Donna Brazile wrote in her memoir she considered invoking after Clinton collapsed two months before the 2016 election.
In her memoir, released a year later, Brazile wrote that she was worried “not just about Hillary’s health but about her anemic campaign ... so lacking in the spirit of fight.”
“Perhaps changing the candidate was a chance to win this thing, to change the playing field in a way that would send Donald Trump scrambling and unable to catch up,” she wrote, adding that aides to other would-be candidates contacted her, including chief of staff to then-Vice President Biden.
But after fewer than 24 hours of consideration, Brazile realized the idea was untenable without Clinton’s cooperation and likely to only divide her party further. “I could not make good on my threat to replace her," she wrote.
Current DNC Chair Jaime Harrison is a longtime Biden ally who serves, essentially, at the pleasure of the president. And the national party has certainly given no indication it’s anything but fully behind the president’s re-election.
What happens if Biden withdraws after the convention?
To fill a vacancy on the national ticket, the DNC chair can call a “special meeting” of the full Democratic National Committee, which includes about 500 members. On paper, at least, all it takes is a majority vote of those present to pick a new presidential and vice presidential nominee. But that process would likely be anything but smooth, and be filled with behind-the-scenes jockeying and public pressure campaigns.
If a vacancy were to occur close to the November election, however, it could raise constitutional, legal and practical concerns. Among other issues, ballots have to be printed well in advance of the election and may not be able to be changed in time.
Would Kamala Harris replace Biden?
If Biden were to relinquish the presidency, Vice President Kamala Harris would automatically become president — but not the Democratic Party’s nominee. Nor would she necessarily be the nominee if Biden withdrew from his re-election bid while remaining in the White House.
She might be politically favored, but party rules give the vice president no major mechanical benefit over other candidates.
Biden’s delegates would not automatically transfer to Harris and the convention holds separate votes on nominees for president and vice president. So she would still need to win a majority of delegates at the convention.
If the top of the ticket was vacated after the convention, she would still need to win a majority of votes at the special meeting of the DNC.
That is all, at least, under current party rules. But a vacancy at the top of the ticket is the kind of dramatic moment that might lead party leaders to revisit them in the name of easing the transition. Harris has some close allies in key places at the DNC, including the co-chair of the party’s Rules and Bylaws Committee. But nothing would likely happen without a fight.
This story first appeared on NBCNews.com. More from NBC News: