A veteran Democrat has publicly called for Joe Biden to withdraw from the election race, as cracks appear in the US President’s support.

Texas representative Lloyd Doggett became the first congressional Democrat to call for Biden to quit, following last week’s widely panned performance in a debate against Republican challenger Donald Trump.

Doggett applauded Biden’s “transformational” first term in office but said it was time to let another member of the party challenge Trump in the November 5 presidential election.

“Recognising that, unlike Trump, President Biden’s first commitment has always been to our country, not himself, I am hopeful that he will make the painful and difficult decision to withdraw. I respectfully call on him to do so,” Doggett said on Wednesday (AEST).

Biden’s campaign did not immediately respond to a request for comment.

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But it came as CNN said it had spoken to more than two dozen current and former Democratic officials, as well as donors and long-time Biden allies.

Although they would not speak on the record, most told the network he should quit – and announce his decision this week.

One, Biden ally Senator Joe Manchin is reported to have become so concerned about Biden after last week’s debate that he considered voicing his worries in a Sunday national TV interview before being convinced otherwise.

Elsewhere, former Speaker Nancy Pelosi told MSNBC that it was “legitimate” to question the candidates on their health.

“I think it’s a legitimate question to say, ‘is this an episode or is this a condition?’ And so when people ask that question, it’s legitimate, of both candidates,” Pelosi said.

Later in the day, a Pelosi spokesman said she had “full confidence in President Biden and looks forward to attending his inauguration on January 20, 2025”.

It followed White House press secretary Karine Jean-Pierre offering a firm “no” to questions on Tuesday about whether Biden has dementia.

“I have an answer for you, are you ready for it?” she said. “It’s no.”

Jean-Pierre then urged the reporter to be sure to ask “the other guy” the same question.

The speculation is unlikely to be helped by Biden’s comments on Wednesday on his debate performance.

Speaking at a campaign event in Virginia, he acknowledged his poor showing.

“I didn’t have my best night, but the fact is that you know, I wasn’t very smart … I decided to travel around the world a couple times, going through around 100 time zones … before … the debate,” he said.

“Didn’t listen to my staff and came back and nearly fell asleep on stage. That’s no excuse but it is an explanation.”

Biden was in France and Italy on two separate trips early in June. He then spent six days at Camp David preparing for the June 27 debate.

Joe Biden with Ukrainian President Volodymyr Zelensky in Paris in June

Biden under scrutiny

Biden’s campaign has hoped to reassure US voters, a majority of whom say they believe he is too old to work in government, that he remains the best choice against his predecessor Trump.

But his stumbling performance during last week’s debate had the opposite effect. His team has since scrambled to reassure key donors that Biden’s appearance was a fluke.

Doggett is the first congressional Democrat to explicitly call for Biden to withdraw, but others have suggested such a move may be worth considering.

“He has to be honest with himself,” Democratic Representative Mike Quigley, a moderate from Illinois, told CNN on Tuesday.

“It’s his decision. I just want him to appreciate at this time just how much it impacts, not just his race, but all the other races coming in November.”

As well as the White House, Democrats are defending vulnerable seats in the Senate, where they hold a 51-49 majority, and are trying to recapture a majority in the House.

Doggett pointed to that dynamic.

“President Biden has continued to run substantially behind Democratic senators in key states and in most polls has trailed Donald Trump,” Doggett said.

“I had hoped that the debate would provide some momentum to change that. It did not.”

A White House official said Biden will meet Democratic governors later on Wednesday.

The meeting, which will be held at the White House but may be largely virtual with governors attending remotely, will give him a chance to reassure leaders in his party that he is of sound mind and body.

Another source said Biden would also meet leaders from Capitol Hill this week, seeking to shore up support among party stalwarts and tamp down talk of stepping aside.

The meetings are part of a broad effort to stabilise his re-election bid after his stumbling display on the Atlanta debate stage.

His team held difficult phone calls on Sunday and Monday with important campaign funders who questioned whether the 81-year-old Democrat should stay in the presidential race.

-with AAP