President Joe Biden on Friday battled to put down an uprising among some Democrats pushing him to abandon his reelection campaign after a poor debate performance, vowing that "I'm staying in the race."

In a fiery speech to supporters in Wisconsin and in an ABC News interview , Biden argued he is the best Democratic candidate to prevent Republican Donald Trump from regaining the White House in the Nov. 5 election.

Biden's halting performance at his debate with Trump on June 27 raised serious concerns among some Democrats about his mental acuity and stamina at age 81.

There is a movement afoot in the party to persuade him to step aside, with critics warning he faces near-certain defeat and could drag other Democrats down with him. House Democrats and a group of senators are expected to convene on the topic when they return to Washington next week.

Some public opinion polls have shown Trump widening a lead since the debate, and a Reuters/Ipsos poll found that one in three Democrats want Biden to quit the race.

Biden rejected the movement on Friday.

"We had a little debate last week. Can’t say it was my best performance. But ever since then there’s been a lot of speculation. ‘What’s Joe gonna do? Is he gonna stay in the race? Is he gonna drop out?" Biden said. "Well here’s my answer: I am running and gonna win again."

Biden used a 22-minute ABC News interview to argue again that he simply had a bad night at the debate but was otherwise fine.

Under persistent questioning from ABC interviewer George Stephanopoulos, Biden dismissed polls that showed him trailing Trump and said other polls have him in a better position.

Asked if he had undergone a specific cognitive test for a neurological exam, Biden said he had not had one and "no one said I had to." The rigors of the White House are sufficient, he said.

In his last physical exam on Feb. 28 he was determined to be fit for duty.

Biden added he was the best candidate to take on Trump and that only "Lord almighty" could oust him from the race.

Biden's latest efforts to convince Democrats to stick with him were dismissed by some, although he seemed determined to fight on.

"He seems not to be able to compute the fact that people have these questions about him," Democratic strategist David Axelrod, a former senior adviser to President Barack Obama, told CNN.

"It’s pretty clear that he’s not going anywhere unless there’s a major revolt on the Hill," a senior Democratic National Committee official told Reuters.

REVOLT ON THE HILL? Senator Mark Warner, a well-respected moderate Democrat, is inviting Democratic senators to a meeting on Monday to discuss Biden's campaign, a source told Reuters. The Washington Post reported Warner was seeking to ask the group to press Biden to exit the race.

Biden told reporters he had spoken to at least 20 lawmakers and that they were telling him to stay. Asked about Warner's call for him to go, Biden said: "Well, Mark Warner, to my understanding, is the only one considering that."

At the rally, Biden said he was thankful for the support of his vice president, Kamala Harris, who has emerged as a top choice to replace him were he to step aside as the Democratic Party's standard-bearer.

One person at the Madison rally held up a sign behind Biden that said, "Pass the torch, Joe."

Harris posted a supportive note on X after the rally, saying Biden had devoted his life to fighting for Americans. "In this moment, I know all of us are ready to fight for him," she said.

But Illinois Democratic Representative Mike Quigley, on MSNBC, called on Biden to step aside and "let someone else do this" or risk "utter catastrophe."

In his appearances on Friday, Biden knocked Trump's intelligence and called him a liar, delivering stinging attacks that were absent when he appeared on the Atlanta debate stage.

But he had sharper words for those in his party who doubt his ability to lead them to victory on Nov. 5.

"They're trying to push me out of the race. Well let me say this as clearly as I can: I'm staying in the race! I'll beat Donald Trump. I will beat him again in 2020," Biden said, getting the year wrong. He followed up by saying: "And by the way we're going to do it again in 2024."

DONORS, BUSINESS LEADERS, ALLIES A handful of donors and business leaders are making their displeasure with Biden's candidacy known loudly, halting funding or looking at possible Democratic alternatives. Even some of Biden's closest political allies, including former Speaker Nancy Pelosi, have raised questions about his health.

Massachusetts Governor Maura Healey issued a statement on Friday asking Biden to weigh the decision carefully, the rare Democratic governor not to issue a statement of support in recent days.

"President Biden saved our democracy in 2020 and has done an outstanding job over the last four years," she said. "The best way forward right now is a decision for the president to make.

Over the coming days, I urge him to listen to the American people and carefully evaluate whether he remains our best hope to defeat Donald Trump."

Trump's campaign and some of his allies have launched a pre-emptive political strike on Harris, moving swiftly to try to discredit her.

Trump, 78, who made multiple false statements during the debate in Atlanta, falsely claimed in a video that was circulated on social media that he had driven Biden out of the race. He made disparaging comments about Harris in the same video, which the Trump campaign stood by.

A group of business and civic leaders urged Biden to end his reelection bid in a letter to the White House on Friday, a day after its CEO said members would still back him if he continued to run, the Washington Post reported.

Biden's former chief of staff, Ron Klain, who led his preparation process ahead of the debate, pushed back against donors' complaints. "We are the Democratic Party!" he wrote on X. Donors "don't get to decide to oust a pro-labor pro-people President." (Reuters)