The former New York City Mayor's decision to drop out comes as he had a dismal showing on Super Tuesday, and had a victory in American Samoa as his only reward for a massive investment.
It was an ugly night for the billionaire US media tycoon who had entered the nomination contest last November with high hopes and deep pockets, investing a record $500 million from his personal fortune into advertising before his name even appeared on a single ballot.
As the candidate who claims he is best positioned to defeat President Donald Trump in November licked his wounds, his campaign signalled to NBC News that Bloomberg will reassess his candidacy Wednesday when a fuller data picture comes in.
Earlier in the day Bloomberg bristled when asked whether a third place was good enough for him -- indicating he considered himself a top three player along with centrist Joe Biden and leftist Bernie Sanders.
But results ultimately showed Bloomberg facing a crushing fourth place finish in no fewer than five of the 14 Super Tuesday states including key battleground Virginia, where he came up empty after reportedly sinking $18 million into advertising and ground operations in the state, dozens of times more than winner Biden invested there.
One consolation: Bloomberg was projected to win in the remote Pacific island territory of American Samoa, hardly the nation's heartland.
"Bloomberg spent $500 million and won American Samoa. Bad business model," one user razzed on Twitter.
The 78-year-old New Yorker told reporters he would not quit the race, insisting he was "in it to win it."
Hours later as results trickled in, Bloomberg put on a brave face.
"No matter how many delegates we win tonight, we have done something nobody thought was possible: in just three months we've gone from one percent of the polls to being a contender for the Democratic nomination," he told supporters at a watch party in Florida.
Millions 'down the drain'
Bloomberg's strategy has been unconventional. He challenged the party custom of campaigning heavily in the four early states of Iowa, New Hampshire, Nevada and South Carolina, opting instead for a Super Tuesday splash.
"While my fellow candidates spent a whole year focusing on the first four states, I was out campaigning against Donald Trump in the states where the election will actually be decided" such as Wisconsin, Michigan, Pennsylvania, Ohio, and Florida, he said.
But the current Democratic race is a battle for a majority of the delegates who pick the nominee at the party's national convention in July.
And while Bloomberg picked up small clumps of delegates in California, Tennessee, Colorado, Texas, Utah and Oklahoma, he is well short of rivals Sanders and Biden, and narrowly trails Senator Elizabeth Warren.
Inescapably, he will face mounting pressure to bow out and clear the way for fellow moderate Biden, whose Tuesday showing made him the definitive challenger to Sanders in the nomination race.
Trump has relentlessly mocked his fellow septuagenarian New York billionaire, and Tuesday was no different.
"The biggest loser tonight, by far, is Mini Mike Bloomberg," the president tweeted, saying his hundreds of millions of dollars in ads went "down the drain."
"He got nothing for it but the nickname Mini Mike, and the complete destruction of his reputation."
Up until Tuesday, Bloomberg had signaled he intended to compete all the way to the Democratic National Convention, which gathers July 13-16 in Milwaukee.
In doing so he acknowledged that his only real possibility of winning the nomination may be a contested convention where no single candidate arrives with the majority of delegates needed to win outright.
Bryce Grahm, a 22-year-old supporter at Bloomberg's Florida event, called him "the best candidate to get the job done, to economically shift this country, to also win against Trump."
Bloomberg's chances were "slim," Grahm acknowledged. "But it's not looking that bad. He is showing on the board."
(with additional reporting from AFP)
