Still, those calls aren't unanimous.

As the chorus of Democratic leaders and donors turning on Biden increases, some wealthy supporters are holding the line because they believe a Biden-Harris ticket is the only viable path to defeat what they view as the greatest threat: Donald Trump.

"The donors that I'm in contact with are solidly behind Biden because we know Biden and Harris can defeat Trump," Ajay Bhutoria, the deputy national finance chair of Biden's National Finance Committee, told Business Insider. The committee consists of hundreds of top Democratic donors.

A spokesperson for the Biden campaign declined to comment on this story, and a Democratic National Committee spokesperson did not respond to a request for comment.

Top donors bail on Biden

Wealthy donors' decision to withhold funds is expected to hit Biden's coffers.

The Biden Victory Fund, a joint fundraising committee, is projected to reel in less than half of the $50 million goal the Biden campaign hoped for, four people familiar with the campaign's finances told The New York Times.

Lauren Hitt, a Biden campaign spokeswoman, told the Times that the number is "speculation" and that totals "mid-month before the final push are meaningless predictors."

Two wealthy donors told BI that they've lost faith in the Biden campaign just in the past month and that a new, younger Democratic nominee is needed to energize the base.

Real estate developer Jeffrey Gural, 82, who has donated $100,000 this year to the party, told BI that Biden's recent debate performance was the final tipping point for his faith in the president's electoral prospects.

"I love Joe. I think he's done an unbelievable job. I just think it's time to give a younger person a chance. I think it'd be difficult for him to win," Gural said.

Another large donor, who had a long-standing relationship with Biden and requested anonymity to speak freely about the campaign, told BI they initially brushed off concerns about Biden's debate performance and were firm in their support for the president.

But on Wednesday, the donor told BI that their thinking, along with other donors they have spoken to, has changed.

"I've evolved the last 12 days. Wasn't just the debate but everything since," the donor told BI in a text message on Wednesday. "Now, no one I know thinks our best option is for Pres Biden to continue."

The donor said that they believed the best option is to choose a new Democratic nominee through an "open mini primary."

Bill Harris, the former CEO of PayPal, told The Washington Post earlier in July that he's spearheading a group of donors who have pledged $2 million to hold debates among potential nominees should Biden step aside.

Choosing a new nominee could energize the party, the donor told BI, naming Vice President Kamala Harris, Sen. Cory Booker of New Jersey, or "another younger Dem" as a few options.

The donor surmised that a new nominee could spark a fundraising bonanza, potentially raising up to $30 million overnight, although they did not explain the thinking behind that number.

Gural told BI that money is no object.

"Money is not the issue here," he said.

Some top donors hold the line

Despite a potential dry spell in wealthy donor money, another member of Biden's national finance committee, who also hosted Biden at their home several years ago and requested anonymity to speak about the campaign, dismissed the impacts of top donors and chastised those backing out on the president.

"Everyone's trying to become relevant in the news cycle by saying something about Biden. Give me a break," they said. "And the donors don't want to give money? Don't give your money. Who cares? He's going to have enough from now to four months from now."

The national finance committee member added that Biden's campaign will rely on grassroots donors and that "top donors don't matter as much as people think."

Biden repeated a similar message in early July, saying in an interview on MSNBC, "I don't care what the millionaires think."

"I'm getting so frustrated by the elites," he said, "I want their support, but that's not the reason I'm running."

Not all top donors have abandoned the Biden-Harris ship.

Amy Goldman Fowler, billionaire real estate heiress who has donated more than $27 million to Democrats in her lifetime, reaffirmed her support for Biden in a statement to The New York Times. She said that she plans to max out her contribution to the Biden Victory Fund with a $400,000 donation.

Retail executive Peter Lowry also donated $929,600 to support Biden's campaign, The Times reported.

Biden's legacy

In making a case for Biden to stay in the running, Bhutoria, the deputy national finance chair, told BI that support for the Biden-Harris ticket also means support for the current administration, naming folks like Defense Secretary Lloyd Austin.

"It's the whole team," Bhutoria said. "And that team is strongly behind Biden."

Both members of the national finance committee who spoke to BI, including Bhutoria, said that choosing a new candidate this far in the race also isn't a viable option.

"You have to refund all the money, you have to fire everyone, rehire everyone. You're four months out. Ballots drop in 90 days. It's a fantasy land," the national finance committee member who requested anonymity said.

But for donors who believed Biden should drop out, the stakes for the 2024 election are too high, not just because of a potential second Trump administration but because of what it may mean for Democrats on Capitol Hill.

"He has two choices," Gural, the real estate developer, told BI. "He can go out on top, or he can stay in the race and most likely lose and take Democrats down in the Senate and House."

CNN reported that some donors, concerned about Biden's impact on down-ballot races, are also threatening to withhold donations to House and Senate races, citing two anonymous sources, including a Democratic strategist involved in big-dollar fundraising.

Gural, who is just several months older than Biden, told BI that he's supported the president for years, spanning back from Biden's run for the Senate in 1972 and Biden's first shot at the presidency in 1988.

"I love Joe," Gural repeated. "I don't know why he wants to roll the dice on his legacy."

Have a tip on the Biden campaign? Reach Lloyd Lee at (646) 768-1630 or email lloydlee.com for his Signal number.