Even for a party accustomed to an anxious donor and political class — a group of second-guessers that Obama adviser David Plouffe famously called the “bed wetters” — billionaire Michael Bloomberg’s likely entry into the Democratic presidential primary has supercharged a debate over whether the party has the right candidates, whether the time for entries has passed, and whether yet other candidates could raise the mountain of cash needed for a credible campaign.

Bloomberg’s decision, fueled by his dissatisfaction with the race’s leading moderate, former vice president Joe Biden, and worries about the rise of liberal leader Elizabeth Warren, injected renewed volatility into the primary race just three months before voting begins with the Iowa caucuses.

Biden’s donors are growing more concerned about his standing — even as some of them begin to write six-figure checks in the hope that a newly formed super PAC can prop up a flagging candidacy that is now further threatened by Bloomberg’s potential entrance. Warren and her allies, meanwhile, welcomed a billionaire foil whom they hope to use to drive home her populist message. Nonetheless, polling this week showing her losing to Trump in critical upper Midwestern states sent a thunderbolt of fear through even some of her boosters.

“It’s a mix in all these cases of three things: nervousness about Warren as a general election candidate, nervousness about Biden as a primary candidate . . . and fundamental nervousness about Trump and somehow the party will blow the race,” said the Democratic consultant David Axelrod. “That’s really a lot of what’s motivating donors and activists.”

Bloomberg’s sudden interest was driven by looming deadlines to file paperwork to get on statewide ballots. The calendar also will force the hand of any other potential entrants, a group that must have either wealth or an existing political network to replicate candidacies that in some cases have been hustling for support for nearly a year.

Names being floated as potential candidates include former Massachusetts governor Deval Patrick and former U.S. attorney general Eric H. Holder Jr. Former secretary of state John F. Kerry, the party’s 2004 nominee, also has been mentioned, although people close to him insist that he will not enter the race.

The party’s 2016 nominee, Hillary Clinton, was fielding calls in recent days about whether to get into the race, some close to her said. While it is still unlikely that she will run, some allies have gone so far as to talk about a potential pathway that would bypass Iowa and New Hampshire and focus on making a stand in South Carolina.

Bloomberg on Friday announced a similar potential plan, with an adviser saying that if Bloomberg did run, he would not aggressively compete in the first four states, an un­or­tho­dox strategy that, for those who have tried it, has led to electoral defeat. The announcement suggested that Bloomberg planned to uncork his campaign for the March 3 Super Tuesday primaries, at which point the race covers multiple states at a staggering cost to candidates.

“The late timing of our entry means that many candidates already have a big head start in the four early states, where they’ve spent months and months campaigning and spending money,” said the Bloomberg adviser, Howard Wolfson. “We have enormous respect for the Democratic primary process and many friends in those states, but our plan is to run a broad-based, national campaign.”

The decision quickly drew scorn from early-state officials, with New Hampshire Democratic Party chairman Ray Buckley saying they were “disappointed and frankly very surprised” by Bloomberg’s move.

“It’s unfortunate that Michael Bloomberg doesn’t want to participate in this invaluable, important and unique primary process and be tested the same way that the other Democratic candidates have been and will be,” Buckley said in a statement.

Not everyone in the party bought into the flurry of worry. Several polls have indicated that Democratic voters are largely satisfied with the current field, although 22 percent of moderates in a Monmouth University survey released Wednesday said they would like to see someone else run — which is twice the number of liberals who feel that way.

“Democrats, we are kvetchers. We kvetch. We are anxious,” said Randi Weingarten, the president of the American Federation of Teachers. “We dwell in our anxiety and our what-ifs. We should just let the process run.”

Biden on Friday became the latest of a parade of candidates to make the trek to the secretary of state’s office in Concord, N.H., for the quadrennial ritual of filing paperwork to get on the ballot.

“Welcome to the race. Michael’s a solid guy. I have no problem with him being in the race,” Biden told reporters about Bloomberg. “Also, in all those states that are swing states, if I’m not mistaken, I’m doing pretty well relative to Trump and relative to all the people running.”

“Look at all the polls,” he added. “I’m leading across the board. And so I don’t quite get this.”

As his campaign sought to project confidence, it made no apparent effort to alleviate the concerns of skittish supporters who have privately begun discussing their worries. Even if they don’t think Bloomberg will become the nominee, they worry about the damage he might do to Biden’s candidacy.

Former Pennsylvania governor Ed Rendell, a prominent Biden backer, said the former vice president needs to perform well in the first four states — Iowa, New Hampshire, Nevada and South Carolina — to fend off Bloomberg, whose candidacy Rendell said could appeal to him and others looking for potential alternatives in case Biden does not have a clear path to the nomination.

“If Joe doesn’t succeed early on, then I think that’s a danger,” Rendell said. “I’m happy that there’s another alternative if Joe doesn’t win.”

Warren on Friday largely avoided any discussion about Democratic skittishness and whether she would do more to answer lingering questions about her general election prospects.

“I’ve done over 150 town halls,” she said in Raleigh, N.C. “I’ve taken thousands of unfiltered questions. I’ve taken tens of thousands of selfies. And it’s about building a movement. I can feel that movement.”

Cincinnati City Council member PG Sittenfeld, who was the first elected official in Ohio to endorse Warren, said that consultants panicking about her electability in the Midwest were misguided.

“No one can convince me that she hasn’t run the best campaign so far by every metric,” Sittenfeld said. “She’s getting the biggest crowds, she’s tied at the top of the polls, she’s tied in fundraising. And I do think there are parts of her biography, of who she is, that aren’t getting amplified yet but would be in a general election.”

Bloomberg’s indication of interest was driven by concerns about the performance of Democratic candidates and worry about the impact on Biden of the impeachment inquiry and of Warren’s handling of Medicare-for-all. Bloomberg’s concern was said to be not just the health-care policy, which is unpopular among some moderate Democrats, but also with Warren’s inability to market it. He saw those factors as likely to reelect Trump.

“He didn’t just wake up and say, ‘Oh my God, the socialists are going to be running the country; I better run for president,’ ” Wolfson said. “He woke up and said, ‘Oh my God, Donald Trump is going to be reelected; I better run for president.’ ”

Bloomberg’s pathway to the nomination is difficult; the former Republican and independent carries substantial baggage from his years as mayor of New York City and from his business career.

A self-financed Bloomberg candidacy would reinforce criticism others in the race have leveled about the disproportionate influence of the wealthy in the American political process.

He has defended stop-and-frisk policing that civil rights groups denounce as racist, has a history of sexual harassment cases at his company that could prove a liability in the #MeToo era and has long been a critic of public labor unions, a key Democratic constituency, when they refuse to renegotiate their pension plans or to weaken workplace protections for teachers in public schools.

He made his money selling technology to Wall Street banks, and he has also been critical of the Dodd-Frank regulation enacted by Democrats under President Barack Obama.

“A field that includes both Elizabeth and Mayor Bloomberg will crystallize the debate over economic inequality and concentrated wealth,” said U.S. Rep. Jamie B. Raskin (D-Md.), a close friend of Warren’s.

But Bloomberg could do significant damage to Biden, whose campaign has already forecast that Biden could lose the early states but would bounce back in South Carolina and on Super Tuesday, when black voters would play a larger role.

By forgoing the early states, Bloomberg could dump significant resources into the states where the most delegates will be amassed even as he helps Warren define herself in ways helpful to attracting liberal voters.

“The two happiest people in America today are Elizabeth Warren and Donald Trump, because every vote that Bloomberg gets is a vote that only Joe Biden would have gotten. That makes Elizabeth Warren happy,” said Biden backer John Morgan, an Orlando lawyer and prominent Democratic donor. “Donald Trump’s ultimate goal is to run against Elizabeth Warren, so it would also make him very happy.”

The undercurrent of Bloomberg’s decision is the widespread sense, even among supporters, that Biden has been a weaker-than-expected primary candidate.

Dick Harpootlian, a Democratic state senator in South Carolina and a longtime Biden supporter, said he donated six figures to the super PAC supporting him, Unite the Country. The super PAC will be in a position “to help dramatically,” he said, estimating that it would spend $10 million to $20 million in the four early states.

“Many people like me who maxed out to the campaign are looking to help, and will write checks to the super PAC,” Harpootlian said. “I sent them six figures. I think other people will do that.”

Biden donor and fundraiser Steve Westly said Bloomberg has bona fide governing experience and net worth that is multiple times greater than Trump’s and could easily self-fund his campaign while appealing to both parties.

“Everybody in the race — Biden, Warren, Trump — needs to take this seriously,” said Westly, a former California state controller and a Silicon Valley investor. Bloomberg “may not be the favorite of the right or the left, but he is formidable.”

Westly said he is heartened to see that Biden has remained near the top in polls, despite his lackluster fundraising. The election results this week showed the “lane in the middle might be bigger than people might understand,” he said.

“It’s good news and bad news for Biden. He has not raised as much money as people had hoped,” Westly said. “But the good news is, he’s continuing to do well in the polls.”

David Weigel and Cleve R. Wootson Jr. contributed to this report.