WEST PALM BEACH, Fla. — Michael R. Bloomberg dropped out of the presidential race on Wednesday, just over three months after he began a campaign that was fueled by his vast fortune and quickly grew to a sprawling political operation but failed to win the groundswell of moderate support he had sought. Mr. Bloomberg endorsed former Vice President Joseph R. Biden Jr., saying that he had the best shot to beat President Trump.
After staking his candidacy on doing well on Super Tuesday, he did not collect on his grand bet, winning only American Samoa.
He made the announcement after falling short in his quest to poach enough center-left voters from Mr. Biden, who carried North Carolina, Virginia and other states across the South on Super Tuesday and won a decisive victory last weekend in South Carolina.
In an unprecedented effort to self-finance a presidential campaign — which some rivals derided as an attempt to buy the White House — Mr. Bloomberg’s bid cost him more than half a billion dollars in advertising alone. He also spent lavishly on robust on-the-ground operations, with more than 200 field offices across the country and thousands of paid staff. His operation dwarfed those of Democratic rivals who ultimately won states in which he had installed many dozens of employees and spent heavily on radio, television and direct mail ads.
Mr. Bloomberg, the former mayor of New York City, exited the race as the Democratic establishment began to converge around Mr. Biden — the very scenario he had judged unlikely when he declared his candidacy in late November. As some of Mr. Biden’s onetime opponents, including Pete Buttigieg, the former mayor of South Bend, Ind., and Senator Amy Klobuchar of Minnesota, endorsed him this week, Mr. Bloomberg’s hopes of capturing the support he needed quickly evaporated.
He was not helped by two deeply unimpressive debate performances, during which Senator Elizabeth Warren of Massachusetts led an onslaught of attacks on his record and past statements. Mr. Bloomberg had difficulty countering criticism that could threaten him in a Democratic primary, on issues including his support for the discriminatory stop-and-frisk policing tactic and his treatment of women in the workplace.
While Mr. Bloomberg’s departure from the race was meant to help unite the Democratic Party — and avoid splintering moderate or independent voters by drawing them away from Mr. Biden — Senator Bernie Sanders of Vermont remained a strong contender in the race and was on track to capture a sizable number of delegates in Tuesday’s contests.
Over the course of his campaign, Mr. Bloomberg had argued against the danger of not just the re-election of President Trump but also the nomination of Mr. Sanders, whom he called incapable of defeating the president. “I don’t think the country wants revolutionary change,” he said this week. “I think the country wants evolutionary change, and Sanders is a very revolutionary kind of guy.”
Mr. Bloomberg spent Super Tuesday in Florida, which will hold its primary on March 17. He acknowledged there that he might not win any states that day and that his only path to the nomination could be through a contested convention.
“I don’t think I can win any other way,” he said at his campaign office in Miami’s Little Havana neighborhood. He was irked by repeated questions about how long he would stay in the race, and whether doing so would benefit Mr. Sanders at the expense of Mr. Biden.
“Joe’s taking votes away from me,” Mr. Bloomberg said, insisting that he had no plans to drop out. “Have you asked Joe whether he’s going to drop out?”
He visited Orlando, where he opened a campaign office and commemorated the victims of the 2016 Pulse nightclub shooting. Then, in what would be his final campaign event, he rallied supporters on Tuesday night in West Palm Beach, promising to compete in upcoming battleground states.
“This is a campaign for change — a campaign for sanity, for honesty, a campaign for inclusion, compassion, for competence, and a campaign for human decency,” he said. “And this is a campaign to bring our country back together and put the ‘United’ back in the United States of America.”
Even as he took himself out of the running, Mr. Bloomberg is likely to remain influential in the 2020 presidential election, having pledged to continue to pour resources into the Democratic effort to unseat Mr. Trump and deploy his main field offices in support of the nominee.
He had pitched himself to voters as “the un-Trump,” often describing himself as “a sane, competent person,” while acknowledging what he called “the elephant in the room” — that a Bloomberg-Trump general election would feature “two New York billionaires” who have played golf together in the past.
“He’s a climate denier, I’m an engineer,” Mr. Bloomberg said repeatedly at his rallies, trying to sharpen the contrasts between himself and the president. “He looks out for people who inherited their wealth, like him, while I’m self-made.”
Along the way, he became a favorite target of Mr. Trump’s on Twitter, with the president posting about Mr. Bloomberg more than 20 times since he entered the race. “Only his highly paid consultants, who are laughing all the way to the bank, still support him,” Mr. Trump wrote this week.
Mr. Bloomberg deployed his wealth to assemble an enormous campaign team of over 2,400 staff members spread across hundreds of offices. He concentrated more than 100 of those offices in Super Tuesday states, where his infrastructure quickly exceeded that of his opponents. For instance, in Ms. Warren’s home state of Massachusetts — where Mr. Bloomberg himself grew up — he established six field offices across the state, four more than Ms. Warren and five more than Mr. Biden, who ultimately won there.
His campaign spent lavishly in other ways, paying staff members unprecedented salaries and seeking to woo voters with slick campaign events that featured swag (tote bags, water bottles, an array of T-shirts in all sizes), drinks (wine, beer, lemonade) and banquet-style food spreads (brisket, cheesesteaks, gourmet flatbread pizzas). They also leveraged the sophistication of Bloomberg LP’s data science, bringing to bear proprietary technology like an artificial intelligence program.
But the very things Mr. Bloomberg called competitive advantages to his candidacy — his moderate politics and dual identity with both sides of the aisle — were also liabilities to his Democratic bid.
Some Democrats attacked his former affiliation with the Republican Party, noting he had won election in New York City on the party’s ticket twice. Ms. Warren in particular took sharp aim at him — denouncing his history of demeaning comments about women, calling on him to release former employees from nondisclosure agreements, and criticizing his past support of Republican candidates like former Senator Scott Brown of Massachusetts, whom Ms. Warren unseated in a tight race in 2012.
Defending his record, Mr. Bloomberg repeatedly invoked his extensive philanthropic support of liberal causes — taking on issues like gun control and climate change — and his support of Democratic candidates. He pointed to the $100 million he had put toward helping the party take control of the House of Representatives in 2018.
But many liberal voters didn’t find his philanthropy persuasive, and Mr. Bloomberg was dogged by criticism relating to past controversies as well as the notion that he was, as Mr. Sanders said, “buying the election.”
Mr. Bloomberg argued that his fortune freed him to focus on issues rather than the horse-trading that can accompany fund-raising, and that his campaign was not beholden to anyone.
“I’m not going to try to be somebody that I’m not,” he said this week before he dropped out of the race. “I can beat Donald Trump, and I don’t know that any of the others can.”
Patricia Mazzei reported from Miami and West Palm Beach, Fla., and Rebecca R. Ruiz and Jeremy W. Peters from New York.