Mr Bloomberg — a former Republican-turned-independent who only registered as a Democrat a year ago — allowed trusted aides to signal that he plans to run, and made a formal announcement last weekend.
“We now need … to ensure that Trump is defeated,” long-time adviser Howard Wolfson declared. “But Mike is increasingly concerned that the current field of candidates is not well positioned to do that.”
Mr Bloomberg’s fears are two-fold. He opted not to join the race in the spring because of the apparent strength of his fellow moderate, former Vice President Joe Biden.
However, a series of lacklustre debate performances, weak fundraising totals and falling poll numbers have dented his aura of invincibility.
At the same time, Mr Bloomberg is apparently concerned that Mr Biden’s travails have strengthened left-wing Senator Elizabeth Warren who, many high-ranking Democrats fear, may capture the party’s nomination but then lose to Donald Trump in the general election.
Mr Bloomberg’s run looks set to provoke a fierce battle for the soul of the Democratic party with fellow Jewish contender, Bernie Sanders.
The socialist senator greeted news that Mr Bloomberg was planning to join the race by tweeting: “The billionaire class is scared and they should be scared.”
Mr Sanders, who has also been losing ground to Mrs Warren, continued his attacks over the weekend, telling a campaign rally in Iowa: “Tonight we say to Michael Bloomberg and other billionaires: Sorry, you ain’t gonna buy this election.”
He appeared to revel in reports that Mr Bloomberg may effectively sit out the first four primary and caucuses — Iowa, New Hampshire, South Carolina and Nevada — and instead focus his efforts on Super Tuesday.
The March 3, 2020 mega-contest when 15 states, including California and Texas will pick their delegates to the Democratic convention, could work to Mr Bloomberg’s advantage.
Unlike the early contests, which require strong grassroots organising, Super Tuesday places a premium on expensive TV advertising.
“When you are worth $50 billion (£39 billion) I guess you don’t have to have town hall meetings and you don’t have to talk to ordinary people,” Mr Sanders declared.
Certainly, Mr Bloomberg’s millions — he is said to be worth $52 billion, dwarfing Mr Trump’s own estimated $3 billion wealth — will free him of the need to spend time fundraising.
The $100 million (£78 million) he ploughed into the Democrats’ successful effort to retake the House of Representatives last November — all but two of the 23 candidates he backed won — also helped him pile up politically useful IOUs.
“There is something about Bloomberg that draws outsized attention,” the Washington Post columnist Dan Baltz argued.
“He does a record of success in business and in politics. He is admired for his competence and his leadership (and his philanthropy) by fellow mayors who have worked with him over the years.”
Some Democrat primary voters will be attracted by the cash — and passion — Mr Bloomberg has poured into campaigns on climate change and gun control.
But, as the party’s grassroots have drifted to the left, the former mayor’s bipartisanship, wealth and past ties to Wall Street, together with the controversial “stop and frisk” powers he gave to New York’s police, may also count against him.
Paradoxically, so, too, might his campaign war-chest: entry to the Democrat primary debates is partly determined by rules requiring a threshold of donors to qualify.
Polls do not indicate a groundswell of support for Mr Bloomberg; a Morning Consult/Politico poll on Saturday suggested four per cent of Democrats would vote for him (although this placed him above 10 other candidates).
He was also viewed more unfavourably by Democrats than any other contender for the nomination.
However, Mr Bloomberg is not only averse to losing, he is a numbers man with a strong data team: he is unlikely to be considering jumping into the contest if he does not see a path to victory.
Indeed, while Mr Trump declared that he would love to take on “little Mike”, the weekend poll also showed the former mayor beating the president by a healthy six points.
That said, while it is easy to see how Mr Bloomberg’s centrist mix of social liberalism and fiscal conservatism might resonate in Republican-leaning suburbs, it might play less well among Midwestern white, working-class voters who helped deliver the White House to Mr Trump in 2016.
Mr Bloomberg’s entry into the race is a gamble — one that risks splitting the moderate vote shared principally between Mr Biden and South Bend mayor Pete Buttigieg. It could assure Mrs Warren’s victory as the nominee.
