WASHINGTON (AP) — President Joe Biden's campaign is insisting anew that he is not stepping aside as he faces the stark reality that many Democrats at the highest levels want him to bow out of the 2024 election to make way for a new nominee and try to prevent widespread party losses in November.

Meanwhile, six more Democratic members of Congress called for him to drop out, making the total now 28..

Isolated as he battles a COVID-19 infection at his beach house in Delaware, Biden's already small circle of confidants before his debate fumbling has shrunk further. The president, who has insisted he can beat Republican Donald Trump, is with family and relying on a few longtime aides as he weighs whether to bow to the mounting pressure.

Biden campaign chair Jen O'Malley Dillion acknowledged "slippage" in support for the president, but insisted he is "absolutely" remaining in the race and that the campaign sees "multiple paths" to beating Trump.

"We have a lot of work to do to reassure the American people that yes he's old, but he can win," she told MSNBC's "Morning Joe" show. But she said voters concerned about Biden's fitness to lead aren't switching to vote for Trump. "They have questions, but they are staying with Joe Biden," she said.

At the same time, the Democratic National Committee 's rulemaking arm opened its meeting Friday, pressing ahead with plans for a virtual roll call before Aug. 7 to nominate the presidential pick, ahead of the party's convention later in the month in Chicago.

"President Biden deserves the respect to have important family conversations with members of the caucus and colleagues in the House and Senate and Democratic leadership and not be battling leaks and press statements," Sen. Chris Coons of Delaware, Biden's closest friend in Congress and his campaign co-chair, told The Associated Press.

It's a pivotal few days for the president and his party: Trump has wrapped up an enthusiastic Republican National Convention in Milwaukee. And Democrats, racing time, are considering the extraordinary possibility of Biden stepping aside for a new presidential nominee before their own convention.

Amid the turmoil, a majority of Democrats think Vice President Kamala Harris would make a good president herself.

A poll from the AP-NORC Center for Public Affairs Research found that about 6 in 10 Democrats believe Harris would do a good job in the top slot. About 2 in 10 Democrats don't believe she would, and another 2 in 10 say they don't know enough to say.

Democrats at the highest levels have been making a critical push for Biden to rethink his election bid, with former President Barack Obama expressing concerns to allies and Speaker Emerita Nancy Pelosi privately telling Biden the party could lose the ability to seize control of the House if he doesn't step away from the 2024 race.

New Mexico Sen. Martin Heinrich on Friday called on Biden to exit the race, making him the third Senate Democrat to do so.

"By passing the torch, he would secure his legacy as one of our nation's greatest leaders and allow us to unite behind a candidate who can best defeat Donald Trump and safeguard the future of our democracy," said Heinrich, who is up for reelection this fall.

And Friday, Reps. Jared Huffman, Mark Veasey, Chuy Garcia and Mark Pocan __ representing a wide swath of the caucus __together called on Biden to step aside.

"We must defeat Donald Trump to save our democracy," they wrote.

Separately, Rep. Sean Casten of Illinois wrote in an op-ed that with "a heavy heart and much personal reflection" he, too, was calling on Biden to "pass the torch to a new generation."

Campaign officials said Biden was even more committed to staying in the race despite the calls for him to go. And senior West Wing aides have had no internal discussions or conversations with the president about Biden dropping out.

On Friday, Biden picked up a key endorsement from the political arm of the Congressional Hispanic Caucus. CHC BOLD PAC said the Biden administration has shown "unwavering commitment" to Latinos and "the stakes couldn't be higher" in this election. "President Joe Biden and Vice President Kamala Harris have delivered for the Latino community," the group said.

But there is also time to reconsider. Biden has been told the campaign is having trouble raising money, and key Democrats see an opportunity as he is away from the campaign for a few days to encourage his exit. Among his Cabinet, some are resigned to the likelihood of him losing in November.

The reporting in this story is based in part on information from almost a dozen people who insisted on anonymity to discuss sensitive private deliberations. The Washington Post first reported on Obama's involvement.

Biden, 81, tested positive for COVID-19 while traveling in Las Vegas earlier this week and is experiencing "mild symptoms" including "general malaise" from the infection, the White House said.

The president himself, in a radio interview taped just before he tested positive, dismissed the idea it was too late for him to recover politically, telling Univision's Luis Sandoval that many people don't focus on the November election until September.

"All the talk about who's leading and where and how, is kind of, you know — everything so far between Trump and me has been basically even," he said in an excerpt of the interview released Thursday.

But in Congress, Democratic lawmakers have begun having private conversations about lining up behind Harris as an alternative. One lawmaker said Biden's own advisers are unable to reach a unanimous recommendation about what he should do. More in Congress are considering joining the others who have called for Biden to drop out. Some prefer an open process for choosing a new presidential nominee.

"It's clear the issue won't go away," said Vermont Sen. Peter Welch, the other Senate Democrat who has publicly said Biden should exit the race. Welch said the current state of party angst — with lawmakers panicking and donors revolting — was "not sustainable."

However, influential Democrats including Senate Majority Leader Chuck Schumer and House Democratic Leader Hakeem Jeffries are sending signals of concern.

"There is of course work to be done, and that in fact is the case because we are an evenly divided country," Jeffries said in an interview on WNYC radio Friday.

But he also said, "The ticket that exists right now is the ticket that we can win on."

He added, "President Biden is correct when he says that he went though a primary process and 14 million or so voters gave him the Democratic nomination. It's his decision to make."

To be sure, many want Biden to stay in the race. But among Democrats nationwide, nearly two-thirds say Biden should step aside and let his party nominate a different candidate, according to an AP-NORC Center for Public Affairs Research poll. That sharply undercuts Biden's post-debate claim that "average Democrats" are still with him.

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Associated Press writers Joey Cappelletti in Lansing, Michigan, Ellen Knickmeyer in Aspen, Colorado, Steve Peoples in Milwaukee, and Josh Boak, Will Weissert, Mary Clare Jalonick, Seung Min Kim and Stephen Groves in Washington contributed to this report.