It is a now decades-old ritual. No sooner are the ballot boxes from the US mid-term elections stowed away, than aspiring presidential candidates — frontrunners, no-hopers and long-shots — begin beating a well-trodden path to Iowa.

The small midwestern state holds the first major test of the presidential primary season: a caucus in January 2020 which matters little in terms of accruing delegates to pick party candidates for the White House, but has assumed huge significance in terms of establishing credibility and momentum.

It is no surprise then that the former New York mayor Michael Bloomberg flew into Iowa last week to host a panel discussion on his new film about climate change.

Mr Bloomberg cares deeply about the issue, but this visit was about much more than global warming. There has been speculation for months that the Jewish billionaire is toying with a run for the presidency.

With the mid-terms over, Mr Bloomberg confirmed he will make a decision early next year on whether to seek the Democratic nomination and run against Donald Trump.

“I think I know why I would want to run. I think I know what I think this country should do and what I would do. But I just don’t know whether it’s possible,” he told AP last month.

Mr Bloomberg is right to be cautious about his chances.

He has considerable assets. With an estimated net worth of $51.8 billion (£41.1 billion), he will have a formidable campaign war chest on tap. Like Mr Trump in 2016, he would also enter the race with high name recognition and the status of a successful businessman and political outsider.

One of the president’s former campaign managers suggested Mr Bloomberg was the “only one” of the likely Democrat candidates who could compete with Mr Trump.

On paper, “Little Mike”, as the president pejoratively labels him, is well-placed to exploit Republican weaknesses. A lifelong Democrat, he switched allegiance when he ran for the New York mayoralty in 2001.

Two years after winning a landslide re-election in 2005, however, the mayor bolted the Republican Party, distressed by its rightward drift on social issues, and won a third term as an independent.

In 2008, 2012 and 2016, Mr Bloomberg was spoken of as a possible centrist, independent candidate who could overcome America’s partisan divisions.

The former mayor chose, however, to keep his powder dry. He endorsed Barack Obama in 2012 and campaigned for Hillary Clinton in 2016, branding Mr Trump a “dangerous demagogue”.

The president appears to have energised Mr Bloomberg. In October, he re-registered as a Democrat, saying the party must provide “the checks and balances our nation so badly needs”.

Mr Bloomberg’s political brand is built on a mix of pro-business fiscal conservatism and social liberalism. He strongly supports abortion rights and same-sex marriage, opposes the death penalty and has attacked the president’s anti-immigration stance.

Mr Bloomberg has also poured considerable sums into the fight for gun control and against climate change.

Such an agenda is likely to play well among educated, white-collar, suburban voters whose strong support enabled the Democrats to take control of the House of Representatives last month.

Mr Bloomberg himself ploughed more than $100 million into Democrat campaigns this year. All but two of the 23 House candidates he backed were victorious, piling up some usefully political IOUs if he does run.

However, the former mayor would face considerable obstacles winning the Democratic nomination.

His centrism and calls for bipartisanship may fail to enthuse a fired-up, left-wing Democratic primary electorate, while his past defence of the banks, support for free trade and ties to Wall Street will come under scrutiny.

So, too, will the controversial “stop and frisk” powers he gave to New York’s police and seemingly supportive remarks he made about a former TV news presenter fired for alleged sexual harassment.

Each will be used to imply he is out-of-step with the Black Lives Matter and Me Too movements.

Indeed, Republican groups already say they’re gathering material on Mr Bloomberg in order to exploit the kind of tensions within the Democratic party which so damaged Mrs Clinton’s run in 2016.

And of course, like Mrs Clinton before him, Mr Bloomberg may also find his cool managerialism pitted against the firebreathing populism of another likely Jewish White House contender: Senator Bernie Sanders.