Bloomberg has a narrow path to winning. But he’ll sure get under Trump’s skin.

It appeared Bloomberg had finally shut the door on that possibility last March. “I believe I would defeat Donald Trump in a general election,” he wrote. “But I am clear-eyed about the difficulty of winning the Democratic nomination in such a crowded field.”

Now comes this: Bloomberg is running after all. Almost certainly. Probably making it official within days.

But who looks at this race and thinks that what it needs is yet another septuagenarian in the mix? Or for that matter, another billionaire? Is the right standard-bearer for an increasingly liberal party a man whose most brilliant business idea was marketing computer terminals to Wall Street traders so that they could make rich people even richer?

Bloomberg changed his mind for two reasons, people close to him say. First is the fact that the early front-runner, former vice president Joe Biden, is turning out to be a substantially weaker candidate than Bloomberg initially assumed. Second is what he believes is the increasingly likely prospect of liberal Sen. Elizabeth Warren (D-Mass.) winning the nomination but running too far to the left to beat President Trump next November.

The ex-mayor’s own polling also shows his own prospects growing more favorable. Since the impeachment inquiry against Trump began, “the emphasis on electability has become even more paramount” among Democratic voters, says Bloomberg adviser Howard Wolfson.

His biography offers Bloomberg, 77, a compelling story to tell. A pragmatic and successful three-term mayor, he can boast a vastly larger fortune than Trump. And unlike the president, he built it without the benefit of family money.

Bloomberg’s speech at the 2016 Democratic convention was a deliciously devastating takedown of Trump’s checkered record of bankruptcies, lawsuits and bad debts. “Trump wants to run the nation like he’s run his business? God help us.” Bloomberg said. “I’m a New Yorker, and I know a con when I see one.”

In recent years, Bloomberg has poured much of his own wealth into favored Democratic causes like fighting for stricter gun laws and against climate change.

He also has built a considerable amount of goodwill with Democrats around the country. Bloomberg and his organizations spent upward of $112 million to help the party’s candidates in last year’s midterm elections. Nor did they stop there. Bloomberg-affiliated groups poured unprecedented amounts into Tuesday’s legislative races in Virginia, which saw Democrats taking control of both houses of the General Assembly for the first time in a generation.

But as a candidate, Bloomberg — a Republican-turned-independent-turned-Democrat — would have to contend with questions about his support for stop-and-frisk policing, his opposition to legalized marijuana and his skepticism of the #MeToo movement.

And as he comes under more scrutiny, there would no doubt be more stories like a scathing profile last year in the Atlantic, in which journalist Megan Garber catalogued allegations that Bloomberg had made “disparaging comments . . . about women’s bodies and appearances” and allowed a “deeply sexist work environment” to exist at the media company he founded and ran for many years.

So where does he see an opening? The premise is that Bloomberg’s path to the nomination, if there is one, would be narrow, untraditional and premised on a Biden collapse.

Rather than looking for victories in the first four state primaries and caucuses, Bloomberg would be counting on Biden to stumble in Iowa, then New Hampshire, then Nevada and South Carolina.

That would leave Biden with no money or momentum as the race heads into the March 3 round of Super Tuesday contests, which in 2020 will include a huge and expensive battle in California. Bloomberg, it is assumed by his strategists, would then be able to tap his own bottomless financial resources to fill a resulting void in the field.

In an election season that has already seen more than its share of surprises, Bloomberg’s probable late entry into a crowded Democratic primary has delivered what is perhaps the biggest one yet.

On Friday, Trump said that Bloomberg “doesn’t have the magic to do well.” But that comment was surely wishful thinking, coming as it did from someone who measures everyone else by their wealth and success. But Bloomberg starts the campaign in a position that is enviable in at least one sense. He is the candidate most likely to get under Trump’s paper-thin skin.

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