WASHINGTON — President Joe Biden’s debate performance has set off alarm bells among top Democrats, leaving some to openly question whether Biden can stay atop of the Democratic ticket.

“He seemed a little disoriented. He did get stronger as the debate went on. But by that time, I think the panic had set in,” longtime Democratic operative and CNN senior political commentator David Axelrod said.

Axelrod also gave voice to a conversation happening among many Democrats on Thursday night: “There are going to be discussions about whether he should continue.”

After a rocky start to the night, campaign and party officials pointed to Biden’s rebuke to former President Donald Trump on the January 6, 2021, attack on the US Capitol as a moment where the president hit his stride. They also noted Biden’s climate change comments and the exchange over Trump’s reported derogatory terms for veterans as high points and argued the president improved as the night went on. Vice President Kamala Harris conceded that the president got off to a “slow start.”

“What we saw tonight is the president making a very clear contrast with Donald Trump on all the issues that matter to the American people. Yes, there was a slow start, but it was a strong finish. And what became very clear through the course of the night is that Joe Biden is fighting on behalf of the American people – on substance, on policy, on performance,” Harris said in an interview with CNN’s Anderson Cooper.

Pressed by Cooper on Biden’s performance, Harris offered a defense of her boss.

“People can debate on style points, but ultimately this election and who is the president of the United States has to be about substance. And the contrast is clear,” she said, pointing to his broader record in office.

“It was a slow start. That’s obvious to everyone. I’m not going to debate that point,” Harris said.

Biden has fielded persistent questions about his age since he decided to make a third run at the White House in 2019. At 81, he is the oldest president in history, and would be 86 at the end of a potential second term. Thursday’s presidential debate on CNN offered a key test for the president to exhibit vigor and energy – and Democratic sources reacting to the debate described emotions ranging from concern to straight-up panic about Biden’s biggest vulnerability.

From the start of the debate, the president appeared to struggle with his voice. Biden cleared his throat or coughed multiple times, a condition that his doctor has previously stated is caused by acid reflux. He has also been battling a cold in recent days, multiple sources told CNN.

Biden often defaulted to an open-mouthed, staring look while Trump was speaking. He occasionally struggled to finish his thoughts or land punches at points, ceding ground on issues like abortion where Democrats have an edge.

Biden brushed off concerns about his debate performance, telling reporters that he thought he performed well while visiting patrons at a Waffle House after the debate.

“I think we did well,” Biden said.

When asked about calls for him to drop out and if he had any concerns about his debate performance, Biden attacked former president Donald Trump.

“No, it’s hard to debate a liar,” Biden said, adding that he has a sore throat.

Thursday’s debate took place before both Biden and Trump are formally nominated at their respective party conventions. The Democratic National Convention convenes August 19 in Chicago.

No serious Democratic challengers have stepped up to run against Biden, and at this point in the campaign, Biden would have to decide to step aside if Democrats were to pick another nominee. If Biden did withdraw, the Democratic nomination would be decided on the floor.

“It’s hard to argue that Biden should be our nominee,” said an operative who’s worked on campaigns at all levels for over a decade.

Democrats were even opining on who it might be instead: “If I was Gavin (Newsom) or Gretchen (Whitmer), I’d be making calls tonight,” one said.

After the debate, Newsom dismissed calls for Biden to be removed from the Democratic ticket.

“I will never turn my back on President Biden. Never turn my back on President Biden, I don’t know a Democrat in my party that would do so,” he said when asked about a rumbling of Democrats possibly open to replacing Biden as the party’s nominee.

“Disaster,” one lawmaker told CNN. “Trump is coming off as reasonable even if he’s lying 60 miles per hour. Biden is unintelligible.”

And one Democrat who’s worked on campaigns up and down the ballot said simply: “We are f**ked.”

Former Biden White House communications director and 2020 deputy campaign manager Kate Bedingfield, also a CNN political commentator, described Thursday’s showdown as an “atypically bad performance” for Biden.

“His biggest issue that he had to prove to the American people was that he had the energy and the stamina. And he didn’t do that,” Bedingfield said, though she described the performance as one bad night with a lot of campaigning left to go.

Other Democrats offered reaction on the style of Biden’s delivery.

“Biden looks and sounds terrible. He’s incoherent,” said one Democrat who spent time working in the Biden administration.

“Horrific,” said another Democratic operative.

Democratic lawmakers watching the debate expressed alarm that the president was not more forceful against Trump’s mistruths, nor clear enough about his own vision and what he’s done for the country.

One Democratic congressman in attendance at a watch party on Capitol Hill with other members told CNN that the moment near the beginning of the debate when Biden was talking about the national debt and appeared to lose his train of thought and pause for several seconds before offering a confusing answer was incredibly tough.

The room, the member said, went silent in shock – and the lawmaker’s own initial reaction was that he wanted to jump off a bridge. Asked to characterize the watch party’s reviews, the member said he and his colleagues have generally felt like Trump appeared young and Biden old; and that Trump was playing mostly offense, while Biden was playing mostly defense.

“He and Jill need to hear what folks are saying” after the debate, “rather than deny them,” one senior Democrat said.

Democrats are especially worried that Trump came across as more measured than usual while Biden was not “punching back” on Trump’s lies.

“I think Joe is doing better than he did in the first 15 minutes, and Trump is just lying his way through the debate. But I wish Joe was a lot stronger punching back,” one lawmaker said midway through the debate.

“It wasn’t great. But that’s why you do this in June. One thousand things will happen between now and Election Day,” another senior Democrat said.

Democratic Party officials questioned why Biden missed other opportunities to slam Trump’s comments, particularly on the issue of abortion.

Another Democratic lawmaker summed up the evening in a text: “Strong on substance, but agonizing presentation.”

Biden advisers were hopeful ahead of the debate that many Americans would watch and see much more than the short clips of Biden on social media that paint him as feeble and weak. There is now a serious concern that that moment where he appeared to lose his train of thought will now be precisely one of those clips that goes viral. — CNN