Can Biden bounce back from rough debate?

Democrats described President Joe Biden's debate performance on Thursday as anywhere from "wobbly" to "disappointing" to a "disaster." Now, they're scrambling to figure out if he can bounce back.

Biden meandered through answers Thursday, seemingly losing his train of thought at points and sporting a slack-jawed, glazed-over expression during former President Donald Trump's answers. The split-screen was described in brutal terms by Democrats who feared the debate compounded on what polls show are undeniable voter concerns over Biden's age and fitness for office.

The president's path to reelection could now hinge, in part, on the tall task of recovering from the debate and reassuring voters that despite his halting performance, he has what it takes to handle another four years in office.

Presidential historian Mark Updegrove singled out one Biden stumble when he appeared lost in an answer about tax reform, ultimately concluding with the confounding remark that "we beat Medicare," as "the worst debate moment in U.S. presidential and vice-presidential history" and said the road to recovery would be difficult -- but not impossible.

"I think this is going to be relatively difficult to turn around," Updegrove said, "but miracles occasionally happen in politics."

The Democratic frenzy in the hours after Thursday night's debate has been fierce, with some operatives bringing up the prospect of replacing Biden on the 2024 ticket at this summer's party convention.

Two aides to politicians spoken of as future presidential candidates told ABC News that outreach from worried party members has been significant, and Democratic offices on Capitol Hill received angry calls from constituents Friday over Biden’s performance, according to one senior congressional Democratic source.

For now, allies are publicly sticking with him.

"I'm with our nominee Joe Biden who wakes up every day thinking about America's working families, not Donald Trump - a 34-time convicted felon, adjudicated rapist, and congenital liar who spent last night spewing nothing but lies," said Illinois Gov. J.B. Pritzker, spoken of as a possible future Democratic presidential contender.

"There's no one who saw the debate last night and thinks that President Biden had a great night. I also know there's no one who can look at the record of the Trump administration and think that Donald Trump had a good presidency," Maryland Gov. Wes Moore, the subject of similar whispers, said to reporters Friday. "I think we're going to have another four years of President Biden and Vice President [Kamala] Harris."

Some Democrats pointed to the 2022 Pennsylvania Senate race, when now-Sen. John Fetterman, D, had what was universally decried as a terrible debate after suffering a stroke only to end up defeating Republican Mehmet Oz later that year.

"No one knows more than me that a rough debate is not the sum total of the person and their record," Fetterman wrote on X. "Chill the f*** out."

Privately, however, Democratic operatives said they're clamoring for Biden to shake things up after Thursday's debate.

One senior Democratic strategist expressed skepticism that Biden's current team "will admit a mistake" and suggested, "perhaps it’s time for some staff changes and infusing the inner circle with fresh perspective."

"Be prepared that there may not be another debate, which means finding another way to demonstrate he’s more than up to the job," the person said. "Would do more to let Joe be Joe rather than trying to cram him with facts and figures."

Other operatives specifically said Biden should blitz the airwaves with sit-down interviews, including in hostile territory -- a tactic the president hasn't adopted since taking office but that party members say is unavoidable now.

"He needs to get out in front of people every day for the next week, conduct live and unscripted interviews, and make the Sunday talk show rounds. This isn’t a time for complacency and the faith that a bad performance fades on its own. It fades when it is replaced by something else," said Jim Kessler, the co-founder of center-left think tank Third Way.

"He'd have to do it across a lot of venues," added another adviser to a politician discussed as a future presidential contender. "He might even have to do one on Fox."

Experts also predicted that the debate's timing could help Biden turn the page. Thursday's event happened unprecedentedly early in an election cycle, and, with over four months to Election Day, countless news cycles could bury the debate if sensational enough.

"In some ways, the early debate could be beneficial for the comeback narrative," said Aaron Kall, director of debate for the University of Michigan's Debate Program. "I think because it's so early, that could decrease the overall impact of a debate on the election and give opportunities other extraneous events, black swan events, to totally drown out the effect of a bad first performance."

Biden is already working to alleviate concerns, addressing the debate at a rally in North Carolina Friday in which he offered a more vociferous defense of his record than he did on Thursday.

"I know I'm not a young man, to state the obvious," he told a Raleigh crowd. "I don't walk as easy as I used to. I don't speak as smoothly as I used to. I don't debate as well as I used to. But I know what I do know: I know how to tell the truth. I know right from wrong. And I know how to do this job."

The Biden campaign also touted a $14 million grassroots fundraising haul from debate day heading into Friday morning. It also said the hour after the debate was its best fundraising hour since the campaign's launch in April 2023.

For some, though, Biden's rally Friday underscored his Thursday performance.

"Where was this last night? Why wasn't that energy there last night?" asked rallygoer Jenny Ackerman.

And some Democrats were outright pessimistic that the debate's political damage wouldn't be permanent.

"I don't think it blows over," a source familiar with the Biden campaign's strategy said.

"Remember the Hindenburg!" added one Democratic donor of the debate.

Underscoring the damage dealt from the debate, Senate Republicans' campaign arm swiftly released an ad splicing Democratic Senate candidates' praise for Biden's fitness for office with moments from the debate when the president stumbled. The made-for-television gaffes are likely to be featured in GOP attacks across the airwaves throughout the year, with Republicans virtually dancing over the debate's impact on both Biden and down-ballot Democrats.

"Senate Democrats have spent years propping up Joe Biden despite his obvious mental deficiencies, now the world can see he isn't he fit for the job. This disaster is on their hands," said National Republican Senatorial Committee spokesman Philip Letsou.

The more pessimistic Democrats pointed to the potency of those attacks to sound the alarm that the damage may have been done.

"It’s hard to unsee what we all saw so starkly and vividly. Think of it this way. Biden may be the most experienced pilot in the world, but would you be comfortable flying in an airplane Captain Biden was at the controls of after what you saw last night?" asked one Democratic pollster.

When asked what Biden could do to calm the passengers, the person just replied, "Turn over the controls to a younger, experienced and competent pilot."

ABC News' Benjamin Siegel and Selina Wang contributed to this report.