After a debate that Joe Biden mumbled his way through, commentators on cable news networks pondered what could happen next.

Could there be a contested Democratic convention? How would that even work? Replacing the president may not be an option, they said, but many acknowledged Democrats are talking about it, spurred by Biden’s troubling debate performance.

MSNBC’s Nicole Wallace laid out how a candidate could release their delegates. Joy Reid said someone sent her the rules.

“The rules are circulating,” Wallace laughed.

“No one is saying it’s going to happen, it’s very unlikely,” Reid reiterated.

The fact that a liberal network would broach the idea of whether an incumbent president running for re-election could be replaced after they’ve won the nomination shows how Democrats are scrambling after the debate to affirm Biden’s ability to lead the nation. Many are questioning whether the party should have serious conservations about what else could be done instead.

From the start, Biden faltered in the debate, the first of the 2024 presidential election. He was hard to hear, mumbling and muffling his lines, some of which – were they delivered with the intended force – could have landed successfully. He said Donald Trump has “the morals of an alley cat”, but even that one-liner was difficult to discern.

Biden had challenged the former president to a debate, set earlier than normal, to shift the momentum of the race. He had delivered a strong State of the Union speech in which he appeared sharp and energetic. A debate could give his campaign some lift at a time when he is polling behind Trump.

Instead of a victory march, or even the more common volleying over who claims to have won the debate, it was clear that Democrats saw Biden’s performance as a liability.

Related: Biden’s poor performance and Trump’s lies: four key takeaways from the debate

Kamala Harris appeared on CNN and MSNBC after to push back and reiterate the reasons voters should side with Biden. She and Gavin Newsom, the California governor and Biden surrogate, both repeatedly talked about how Trump lied and deflected throughout the debate – and sought to remind voters what a Trump presidency was like and could be again.

“It was a slow start, there’s no question about that, but I thought it was a strong finish,” the vice-president said on MSNBC before launching into a list of Biden’s accomplishments, saying Biden fights for the people while Trump fights for himself.

Newsom, on MSNBC, called the questions “unhelpful” and “unnecessary”. The conversations are “rabbit holes” that detract from Biden’s record and hinder democracy and the country’s fate.

“We’ve got to have the back of this president,” Newsom said. “You don’t turn your back because of one performance. What kind of party does that?”

The assurances came as Democratic operatives and officials, both publicly and behind the scenes, fretted over their prospects in November after a debate where Biden’s age and sharpness, his biggest liability, took center stage.

David Plouffe, a Democratic strategist and former Obama campaign official, called the debate “kind of a Defcon 1 moment”.

“The biggest thing in this election is voters’ concerns – and it’s both swing voters and base voters – with his age, and those were compounded tonight,” Plouffe said.

Democrats laid out ways the Biden camp could turn the moment back toward him and get his performance out of voters’ minds: send out his surrogates to support him, put strong speakers like Harris or Newsom on the morning shows, announce an initiative or endorsement or big idea. Anything to change the narrative.

The stakes of this election – the fate of democracy itself – underscore how important Democrats see a win in November, and how worried they are that Biden could lose to Trump, who represents an attack on their most basic values.

Maria Shriver, the former first lady of California, said she loves Biden and knows he’s a good man, but the evening was “heartbreaking in many ways”.

“This is a big political moment. There’s panic in the Democratic party. It’s going to be a long night.”

Related: Biden struggles to land lines as Trump lies in first presidential debate

Nicholas Kristof, the leftwing political columnist, said on Twitter/X that he hopes Biden reflects on the debate and decides to withdraw from the race, letting the convention decide who should be the nominee. He suggested someone like Michigan governor Gretchen Whitmer, Ohio senator Sherrod Brown or commerce secretary Gina Raimondo.

Former Missouri senator Claire McCaskill said on MSNBC that Biden had one job, and he didn’t do it: He needed to “reassure America that he was up to the job at his age, and he failed”. Democrats are doing more than hand-wringing in private and wondering why the Biden surrogates, who were performing well to counter the Biden debate performance, aren’t the ones at the top of the ticket, she said.

“I know how this felt tonight: it felt like a gut punch,” McCaskill said.