Biden met for more than an hour at the White House in person and virtually with more than 20 governors from his party. The governors told reporters afterward that the conversation was "candid" and said they expressed concerns about Biden's debate performance last week.

But they did not join other Democrats in urging him to leave the race.

"The president is our nominee. The president is our party leader," said Gov. Wes Moore of Maryland. He added that, in the meeting, Biden "was very clear that he's in this to win it."

THIS IS A BREAKING NEWS UPDATE. AP's earlier story follows below.

WASHINGTON (AP) -- A defiant President Joe Biden vowed Wednesday to keep running for reelection, rejecting growing pressure from Democrats to withdraw after a disastrous debate performance raised questions about his readiness to keep campaigning, much less win in November.

But increasingly ominous signs were mounting for the president. Two Democratic lawmakers have called on Biden to exit the race while a leading ally publicly suggested how the party might choose someone else. And senior aides said they believed he might only have a matter of days to show he was up to the challenge before anxiety in the party boils over.

"Let me say this as clearly as I possibly can as simply and straightforward as I can: I am running ... no one's pushing me out," Biden said on a call with staffers from his reelection campaign. "I'm not leaving. I'm in this race to the end and we're going to win."

Still, despite his efforts to pull multiple levers -- whether it was his impromptu appearance with campaign aides, private conversations with senior lawmakers, a weekend blitz of travel and a network television interview -- to salvage his faltering reelection, Biden was confronting serious and mounting indications that support for him was rapidly eroding on Capitol Hill and among other allies.

Rep. Raul Grijalva, D-Ariz., told The New York Times that though he backs Biden as long as he is a candidate, this "is an opportunity to look elsewhere" and what Biden "needs to do is shoulder the responsibility for keeping that seat -- and part of that responsibility is to get out of this race."

Senior aides said they believe the 81-year-old Biden has just a matter of days to mount a convincing display of his fitness for office before his party's panic over his debate performance and anger about his response boils over, according to two people with knowledge who insisted on anonymity to more freely discuss The president accepts the urgency of the task -- having reviewed the polling and mountains of media coverage -- but he is convinced he can do that in the coming days and insistent that he will not step out of the race, the aides said.

Meanwhile, a major Democratic donor, Netflix co-founder Reed Hastings, also called on the president to exit the race, saying, "Biden needs to step aside to allow a vigorous Democratic leader to beat Trump and keep us safe and prosperous." The statement was first reported by The New York Times.

And all that followed Rep. Jim Clyburn, a longtime Biden friend and confidant, saying he'd back a "mini-primary" in the run-up to the Democratic National Convention next month if Biden were to leave the race. The South Carolina Democrat floated an idea that appeared to be laying the groundwork for alternative choices by delegates during the Democrats' planned virtual roll call that is scheduled before the more formal party convention set to begin Aug. 19 in Chicago.

On CNN, Clyburn said Vice President Kamala Harris, governors and others could join the competition: "It would be fair to everybody."

Clyburn, a senior lawmaker who is a former member of his party's House leadership team, said he has not personally seen the president act as he did on the debate stage last week and called it "concerning."

And even as other Democratic allies have remained quiet since Thursday's debate, there is a growing private frustration about the Biden campaign's response to his disastrous debate performance at a crucial moment in the campaign -- particularly in Biden waiting several days to do direct damage control with senior members of his own party.

One Democratic aide said the lacking response has been worse than the debate performance itself, saying lawmakers who support Biden want to see him directly combatting the concerns about his stamina in front of reporters and voters. The aide was granted anonymity to candidly discuss interparty dynamics.

Most Democratic lawmakers are taking a wait-and-see approach with Biden, though, holding out for a better idea of how the situation plays out through new polling and Biden's scheduled ABC News interview, according to Democratic lawmakers who requested anonymity to speak bluntly about the president.

When Texas Rep. Lloyd Doggett, who called on Biden to leave the race this week, shopped around his move for support from other Democratic lawmakers, he had no takers and eventually issued a statement on his own, according to a person familiar with the effort granted anonymity to discuss it.

But there was also a sense that the waiting period will soon expire if Biden does not step up his outreach to Capitol Hill or prove otherwise that he's up to the job.

Some suggested Harris was emerging as the favorite to replace Biden if he were to withdraw, although those involved in private discussions acknowledge that Govs. Gavin Newsom of California and Gretchen Whitmer of Michigan remain viable alternatives. But for some insiders, Harris is viewed as the best prospect to quickly unify the party and avoid a messy and divisive convention fight.

Even as pressure around Biden mounted, he and Harris made a surprise appearance on an all-staff reelection campaign call and offered a pep talk. They stressed how important it was to beat former President Donald Trump, the presumptive nominee, in November and returned to Biden's previous post-debate vow that when he gets knocked down, he gets up again.

"Just as we beat Donald Trump in 2020, we're going to beat him again in 2024," said Biden, who told participants that he would not be dragged out of the race. Harris added: "We will not back down. We will follow our president's lead. We will fight, and we will win."

White House press secretary Karine Jean-Pierre was asked during her briefing with reporters whether Biden would consider stepping down. "Absolutely not," she said.

"I cannot lay out something that would change the president's mind," Jean-Pierre said about Biden continuing to seek a second term. She added that he "is clear-eyed. And he is staying in the race."

Still, Democrats are unsatisfied with the explanations of Biden's debate performance, from both White House staff and the president himself. And there is a deeper frustration among some in the party who feel that Biden should have handled questions about his stumbling debate performance much sooner and that he has put them in a difficult position by staying in the race.

The Leadership Now Project, a group of business executives, academics and thought leaders, said in a letter that the "threat of a second Trump term" is great enough that Biden should "pass the torch of this year's presidential nomination to the next generation of highly capable Democrats."

Trump's campaign issued a statement noting that "every Democrat" now calling on the president "to quit was once a supporter of Biden."

Trump had a slight lead over Biden in two polls of voters conducted after last week's debate. One poll, conducted by SSRS for CNN, found that three-quarters of voters -- including more than half of Democratic voters -- said the party has a better chance of winning the presidency in November with a candidate other than Biden.

About 7 in 10 voters, and 45% of Democrats, said Biden's physical and mental ability is a reason to vote against him, according to the CNN/SSRS poll.

And about 6 in 10 voters, including about one-quarter of Democrats, said reelecting Biden would be a risky choice for the country rather than a safe one, according to a New York Times/Siena College poll. That poll found that Democrats were split on whether Biden should remain the nominee.

Biden campaign pollster Molly Murphy said "today's polling doesn't fundamentally change the course of the race."

In a further effort to boost morale, Biden chief of staff Jeff Zients urged White House aides during an all-staff meeting to tune out the "noise" and focus on the task of governing.

Biden himself began making personal outreach on his own, speaking privately with senior Democratic lawmakers such as Senate Majority Leader Chuck Schumer of New York, House Minority Leader Hakeem Jeffries of New York, former House Speaker Nancy Pelosi, Delaware Sen. Chris Coons and Clyburn.

Among the Democratic governors who were planning to attend in person were Tim Walz of Minnesota, who leads the Democratic Governors Association, Newsom, Whitmer, J.B. Pritzker of Illinois, Maura Healey of Massachusetts, Daniel McKee of Rhode Island, Andy Beshear of Kentucky, John Carney of Delaware and Wes Moore of Maryland, according to their aides. Govs. Roy Cooper of North Carolina, Josh Shapiro of Pennsylvania, Jay Inslee of Washington, Jared Polis of Colorado, Tina Kotek of Oregon and Phil Murphy of New Jersey were planning on attending virtually. Harris will also attend the session with governors.

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Associated Press writers Mary Clare Jalonick, Zeke Miller, Colleen Long, Josh Boak and Amelia Thomson-DeVeaux in Washington and Michael Liedtke in San Francisco contributed to this report.