WASHINGTON (AP) — A defiant President Joe Biden vowed on Wednesday to keep running for reelection, rejecting growing pressure from Democrats to withdraw after a disastrous debate performance raised questions about his readiness. But, in an ominous sign for the president, a leading ally publicly suggested a way that the party might choose someone else.

“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.”

The president was pulling every possible lever to try to salvage his reelection campaign — talking to top legislators, pumping up his campaign staff and meeting later in the day with Democratic governors before a planned weekend blitz of travel and a network TV interview.

But there were mounting signs that support for Biden was rapidly eroding among Democrats on Capitol Hill.

Rep. Jim Clyburn, a longtime Biden friend and confidant, said he would back a “mini-primary” in the run-up to the Democratic National Convention next month if Biden were to leave the race. Clyburn, a South Carolina Democrat, floated an idea that appeared to be laying the groundwork for alternatives by delegates during the Democrats’ planned virtual roll call that is scheduled before the more formal party convention, which is set to begin Aug. 19 in Chicago.

“You can actually fashion the process that’s already in place to make it a mini-primary and I would support that,” Clyburn told CNN.

He said that Vice President Kamala Harris, governors and others could join the competition. “It would be fair to everybody. … Because if she were to be the nominee we need to have a running mate. And need a strong running mate.”

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.

“I saw what I saw last Thursday night, and it is concerning,” Clyburn said.

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 a short time later 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 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 House Democratic leadership planned an evening call, and 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.

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, Delaware Sen. Chris Coons and Clyburn.

Zients tried to rally the staff’s confidence in Biden’s reelection apparatus and said Biden has always made it through tough times, despite being counted out over his decades in public office.

The chief of staff also encouraged aides to “continue being a team” and, while acknowledging the increasing political chatter, to “tune it out” and stay disciplined, according to the official, who was granted anonymity to relay Zients’ private remarks.

Staff-wide White House calls aren’t unusual, but Wednesday’s came as Biden and senior White House officials were working to assuage rattled lawmakers, donors and other allies within the party amid sharpening questions about whether the 81-year-old president had the competency to run for a second term in office.

Biden and Harris also held one of their occasional lunches, and the president was hosting an assortment of Democratic governors at the White House in the evening.

Among the Democratic governors who were planning to attend in person were Tim Walz of Minnesota, who leads the Democratic Governors Association, J.B. Pritzker of Illinois, Maura Healey of Massachusetts, Daniel McKee of Rhode Island, Gretchen Whitmer of Michigan, Andy Beshear of Kentucky, Wes Moore of Maryland and Gavin Newsom of California, according to their aides. North Carolina Gov. Roy Cooper and New Jersey Gov. Phil Murphy were planning on attending virtually.