Major donors are turning on Biden. Quietly.

Wealthy Democratic donors who believe another nominee would be the party’s best chance to retain the White House are increasingly silent about President Biden, worried that any action against him could backfire.

On Tuesday night, the party’s wealthy class kept a close eye on post-debate polls and the standing of elected Democrats to see if support for Biden was waning.

Previous attempts by donors to campaign on their own to pressure Biden to step down as the party’s presidential nominee have failed or drawn opposition from other donors and aides.

The impasse is a sign of a broader paralysis within the party over how to deal with a tense situation that could divide the party, alienate key voters, damage personal relationships and benefit a Republican candidate who most donors see as a threat to democracy.

The dynamics began to take shape just hours after the debate.

At a breakfast Friday morning at the Hotel Jerome in Aspen, Colo., where nearly 50 Democratic donors had gathered for a pre-scheduled meeting called by the super PAC American Bridge, someone asked the crowd to raise their hands to indicate how many thought Mr. Biden should step aside. Nearly everyone in the room raised their hands, according to two attendees.

Some members of the Democracy Alliance network of liberal financiers proposed a public statement calling on Mr. Biden to resign, sparking a heated debate among some members of the group, with some flashing their dream tickets. But the group’s board met after the debate and decided to uphold its support for Mr. Biden, according to a person with knowledge of the decision.

On a closed email list of members of another liberal donor collective, Way to Win, participants expressed frustration with the way the Democratic Party was rallying around Biden and urged Vice President Kamala Harris to be considered for the top spot on the list.

A small, closed online survey distributed to liberal donors and their advisers after the debate found that of dozens of respondents, more than 70 percent said they were “ready to explore Plan B.”

And on Wall Street, some of Biden’s wealthiest former backers — including Seth Klarman, the billionaire CEO of the hedge fund Baupost and a sharp critic of former President Donald J. Trump — have privately discussed whether to look beyond Biden, according to two people familiar with his thinking.

On Tuesday, both American Bridge and the Democracy Alliance held calls for donors concerned about the situation. Of the more than a dozen donors who spoke on the Bridge call, only one argued that the party should stick with Mr. Biden, according to one participant. Others indicated they wanted to move on.

And next week, the dilemma is expected to be a hot topic at the annual meeting of CEOs at the Allen & Company Summit in Sun Valley, Idaho, a source close to several major donors said.

The deliberations among wealthy Democrats, detailed in more than two dozen interviews and written communications seen by The New York Times, only grew more heated as Biden’s campaign and party leadership formed a protective wall around him in the days after the debate.

The party’s aggressive defense of Biden has deterred donors from publicly calling for his replacement, said Maggie Kulyk, a wealth management firm owner and board member of the Women Donors Network.

“If we follow this line, we’ll look almost, but not quite, as morally bankrupt as the Republican Party,” she said. “Come on, man! Know when to say when.”

Ms. Kulyk added that donor coalitions may be reluctant to engage with Mr. Biden because they don’t want to alienate donors “who feel strongly that we should just stay the course.”

But, she said, “I don’t think the wall is very strong,” adding, “if a few votes came up, it could all fall apart. And in my mind, I think that’s what needs to happen.”

Donor support is one closely watched indicator of whether Mr. Biden can survive the mounting doubts that have surrounded his weak debate performance. Other factors include the positions of elected Democrats, some of whom began questioning Tuesday whether it is in the party’s interest to back Mr. Biden, and post-debate polling.

The support of major donors is important to Mr. Biden. Both Mr. Trump and Mr. Biden have used digital fundraising to their advantage during difficult moments, such as Mr. Biden’s disastrous debate and Mr. Trump’s conviction. But it’s the seven-figure donors who are essential to funding negative ads by super PACs, for example.

The Biden team, and some donors themselves, are not happy with the suggestion that big donors could force a change in the ticket.

“It’s scary to suggest that the donor community could do that,” said Craig Kaplan, a lawyer and Democratic donor in New York. “Money plays too big a role in politics as it is.”

The debate has particularly divided Democratic donor groups, which are usually fairly harmonious. At Way to Win, a donor alliance formed at the height of the Trump-era backlash, leaders of the organization have touted Ms. Harris as a possible replacement for Mr. Biden.

Jen Fernandez Ancona, a founder of the group, stressed Ms. Harris’s electoral viability to allies in an internal email chain reviewed by The Times: “I absolutely believe we can do it with Harris at the top of a ticket and a good choice for vice president.”

Tory Gavito, another founder of Way to Win, said in an interview that the organization’s official position went no further than calling on Ms. Harris to take the lead.

If Mr. Biden were to withdraw and Ms. Harris were to rise to the top of the ticket, she would inherit the campaign’s cash reserves, which stood at $212 million as of last month. If another candidate were to rise to the top of the ticket, things could get more complicated. “Think about it carefully,” said Steve Silberstein, a major Democratic donor. “You have to think three moves ahead in this game.”

Democratic donors have been vigorously debating potential replacements alongside Ms. Harris, including Gov. Gavin Newsom of California and Gov. Gretchen Whitmer of Michigan. Some donors have reached out to Mr. Newsom to encourage him to run, according to a person familiar with the outreach.

In Silicon Valley, efforts by Reid Hoffman, the billionaire founder of LinkedIn, to rally fellow Silicon Valley donors behind Biden have been controversial among his peers. In an email blast this week, an adviser to Hoffman criticized Way to Win and the Democracy Alliance.

A billionaire megadonor similar to Mr. Hoffman called an email he sent trying to minimize the impact of the debate “shocking.” And some other donors who received the email said he was too dismissive of the risks of keeping Mr. Biden as the nominee, according to two people close to other major donors. Tech entrepreneurs who have privately dismissed Mr. Biden’s chances include investor Ron Conway and StubHub CEO Eric Baker, according to people close to them.

On Wall Street, where executives are typically unsentimental about taking losses, a half-dozen prominent Democratic donors said Biden’s chances had plummeted after the debate, sometimes using profanities to describe the situation.

In recent days, several Democratic Party business leaders and political operatives have called JPMorgan Chase CEO Jamie Dimon, according to a person with knowledge of the calls, to gauge his interest in replacing Biden. (Dimon has repeatedly said he will not run.)

Michael Novogratz, a cryptocurrency investor who backed Biden in 2020 but now worries about his age, welcomed the moment. “I’ve been advocating for other choices,” he wrote in a text to The Times. “The poor performance at the debate opened that door for the first time.”

Mr. Klarman, the hedge-fund manager and a staunch supporter of Mr. Biden in the run-up to the debate, has been telling friends and fellow donors in recent days to seriously consider exploring a Plan B, citing his performance at the debate, according to a person who spoke to him.

“The most important thing President Biden — and all of us who have supported him this far — can do is prioritize defeating Donald Trump in this election,” Klarman said in a statement. “I trust that President Biden, who has been a truly great president, will continue to make this central to every decision about the path forward.”

Some donors and their political advisers said in interviews that Democrats would be better off focusing on groups that can help the party, regardless of who tops the ticket.

Steve Phillips, a longtime Democratic donor in San Francisco who described himself as “inundated with frantic phone calls, emails and texts from other Democratic donors desperate for a way to take Biden off the presidential ticket,” said he had advised his colleagues to “just sit tight, ride this out and focus on voter mobilization.” He added: “That’s a much better use of your time than worrying about whether Gretchen Whitmer might be the nominee.”

Donors pushing for Biden to be replaced should be careful what they wish for, warned John Morgan, a lawyer who said he has raised nearly $1 million for Biden’s campaign and was planning a summer fundraiser for Biden.

“I fear that the scrum for a new nominee could create more infighting and do more harm than good to the overall plan,” Mr. Morgan wrote in a text. “None of us will decide — the President will.”

Still, the president’s outside supporters and their donors are beginning to consider how they might change course without Mr. Biden. The billionaire Facebook co-founder Dustin Moskovitz, one of the party’s biggest donors, was asked on social media Tuesday what the party should do with Mr. Biden.

“Ah, that’s easy, they just have to do it,” said Mr. Moskovitz jokedcutting himself off in mid-sentence. He didn’t write another word.