Biden’s collapse would likely leave Elizabeth Warren as front runner, a liberal candidate with whom he has repeatedly clashed over her anti-corporate policies and fears she will push the party too far to the left and eliminate the chance of a Democratic candidate unseating Donald Trump next year.

Bloomberg’s disagreements with Warren are stark. In January, when he was considering a run for president, he described Warren’s wealth tax proposals in extreme terms.

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“We shouldn’t be embarrassed about our system,” he said.

“You want to look at a system that’s not capitalistic, just take a look at what was perhaps the wealthiest country in the world and now people are starving to death. It’s called Venezuela.”

More recently, at an anti-gun event in Iowa hosted by the Everytown for Gun Safety Action Fund, a group Bloomberg founded and supports, he was again asked about Warren’s wealth tax proposals.

“I just said to Senator Warren on the way out, ‘Senator, congratulations, it’s a nice talk. But let me just remind you if my company hadn’t been successful, we wouldn’t be here today, so enough with this stuff’,” he said.

Bloomberg’s attitude to wealth is diametrically opposed to Warren, whose criticisms of the financial sector’s excesses are legion. Before he ever ran for New York mayor, his company threw a party in London complete with entertainers – representing avarice – instructed to wave bundles of cash and shout: ‘Money, ain’t it gorgeous?’

Forbes recently put his wealth at US$51 billion.

Bloomberg has previously flirted with presidential ambitions, but he decided not to run in 2016 after concluding he might split the Democratic vote. It is not clear that dynamic has changed, nor whether Democratic primary voters really have the taste for a billionaire candidate.

But others see a possible centrist path to the White House.

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“The reality is both parties, Republican and Democrat, are in serious trouble, they are not functioning, and they’ve gone to extremes,” says veteran strategist Hank Sheinkopf.

“Could Mike Bloomberg unite the centre of the party and bring people to the centre if he can prove he can win? The answer is yes.”

“Bloomberg has up-top professionals ready if he needs them, and he could assemble an operation in days and go to work. Whether the Democrats like him as centrist or not, they want to win the White House. He provides an extraordinary alternative to losing.”

People familiar with Bloomberg’s thinking says his aims are clear – and they’re grouped neatly as gun control, climate change, coal, education and health.

“He doesn’t understand why people don’t talk about his five points more. If he happens to mention something about the presidency at a cocktail party and they get talked about more, that’s a good thing for him,” one source said.

Strengthening the rumour mill is Bloomberg’s appointment of his former deputy Patti Harris to his company’s management committee. Harris has been at the company since 1994.

As Bloomberg’s deputy during his three terms as New York mayor, Harris was regarded, in personal and political terms, as the keeper of the Bloomberg brand, his personal gate keeper and point person on all strategic and staffing decisions.

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“She’s the most important person in his life and director of all his political aspiration,” says the source. “If you believe in this line of gossip, putting Harris in to run the company frees him up to run for president. You can argue that he’s setting himself up to do something.”

When Bloomberg was last considering a run, almost exactly a year ago, a Quinnipiac University poll found he had an overall unfavourable rating of 32 per cent, and 19 per cent of Democrats viewed him negatively.

Howard Wolfson, a top political adviser, hinted at how much Bloomberg would look to invest in a campaign for president.

“Mike spent more than US$100 million in his last mayor’s race. Last time I looked, NYC is a fraction of the size of the country as a whole,” Wolfson explained, pointing out that he spent at least more than US$110 million backing Democrats during the 2018 congressional midterm elections.

Asked what Bloomberg would spend on his own campaign, Wolfson replied: “Whatever is required”.

With Biden appearing to be running low on funds, and a Warren or possibly Bernie Sanders candidacy looming, it’s not surprising that Bloomberg’s interest is again stirring. Last month, Fox Business reported that he still has a team of political advisers on the payroll.

“I think it’s something he wants. He has not been shy about that,” a Bloomberg ally told CNBC.

“Bloomberg is in if Biden is out,” a billionaire friend added.