• President Joe Biden's widely panned debate performance against former President Donald Trump stoked panic among Democrats.
• Liberal commentators and top Democratic donors are weighing whether to push to replace Biden as the party's nominee.
• But Biden aides and leading Democrats say he is committed to running for a second White House term against the Republican Trump.

President Joe Biden's raspy, unfocused, often inarticulate and widely panned debate performance stoked deep anxiety among Democrats — and caused some commentators and fundraisers to openly call for a new nominee to run against former President Donald Trump.

But replacing Biden as the party's pick less than five months out from Election Day carries enormous political risks and would be difficult, if not impossible, to pull off.

Right now, the only likely way Biden could be replaced is if he willingly ends his campaign.

And Biden's aides and top Democratic officials say the 81-year-old incumbent has no plans to do so.

If he did drop out, Democrats have yet to identify a clear alternative candidate to swap in.

But the panic among donors and party officials after watching Biden falter Thursday night in his debate against Trump has led some of them to take steps to get Biden out of the race.

There are already discussions among Democratic fundraisers about trying to convince congressional leaders — Senate Majority Leader Chuck Schumer in particular — to urge Biden to announce to drop out, according to people familiar with the matter who were granted anonymity to speak freely.

Schumer, D-N.Y., is a top target for donors making that pitch because he privately has voiced concerns about Biden's standings in presidential election polls, those people said.

Schumer was worried before the debate that Biden and Trump were statistically tied nationally, despite the Republican challenger's conviction in his New York criminal hush money trial.

A spokesman for Schumer declined to comment to CNBC but pointed to a social media post the majority leader published after the debate.

Schumer in that X post wrote: "Tonight's debate made the choice clear: Four more years of progress, or four more years of attacks on our fundamental rights and our democracy."

"We've got to get out the vote for Joe Biden, Kamala Harris, and a Democratic Senate and House!" the post said.

That spin has not alleviated the post-debate anxiety felt by some of the president's top fundraisers.

Some of those wealthy donors have lost trust in Biden's team, believing they were given false assurances about Biden's ability to take on Trump.

And some of those donors who already planned to attend a high-dollar fundraiser Saturday in the Hamptons section of Long Island say they will attend the event to judge for themselves whether Biden can continue as a viable candidate.

"Democrats are in a very difficult situation because it's late in the campaign for a change," said Meena Bose, director of the Peter S. Kalikow Center for the Study of the American Presidency at Hofstra University, in an interview with CNBC.

The only feasible way Bose could see it playing out is with Biden throwing his full support behind Vice President Kamala Harris to become the new nominee.

Otherwise, Democrats have a wide-open nomination fight just a few months before the Nov. 5 election, she said.

Bose called that a "disastrous" prospect."

"Vice President Harris is a risky choice, but certainly has the visibility and is the logical choice," said Bose.

"It's difficult to see how you open up the Democratic presidential nomination now and have a unified path to victory in November," she added.

However, even if Biden backed Harris to replace him ahead of the Democratic National Convention in August, there is no guarantee that the delegates he has won so far will shift their support to her.

Biden has won nearly all of the roughly 4,000 Democratic-pledged delegates, far exceeding the threshold to make him the party nominee.

If Biden refuses to drop out before August, the only opportunity to boot him as nominee would be at the Democratic National Convention that month.

It is technically possible that Biden's delegates could abandon him en masse then and throw open the convention to nominate another candidate.

Some Democrats who want an alternative to Biden but are concerned about Harris' relatively low opinion polls and rocky campaign history have looked to California Gov. Gavin Newsom, Ohio Sen. Sherrod Brown, Illinois Gov. J.B. Pritzker and others as possible contenders.

But blocking Biden from the nomination is highly improbable, as delegates tend to be strong supporters of their chosen candidate.

"That is probably the worst-case scenario," Bose said. "If the Democrats are going to have a change at the top of the ticket, President Biden has to endorse it and, frankly, probably initiate it."

The DNC rules allow for the party to select another presidential nominee, but only in the "event of death, resignation or disability" that leaves the role vacant.

Biden at a rally in North Carolina on Friday afternoon acknowledged his subpar debate performance but defended his ability to win and serve as president.

"I know I'm not a young man, to state the obvious," Biden told a cheering crowd. "I don't walk as easily as I used to, I don't speak as smoothly as I used to, I don't debate as well as I used to."

"But I know what I do know: I know how to tell the truth, I know right from wrong, I know how to do this job, I know how to get things done," he said.

"I know, like millions of Americans know, when you get knocked down you get back up," he said. "I give you my word as a Biden I would not be running again if I didn't believe with all my heart and soul I can do this job because quite frankly, the stakes are too high."