It is called the “invisible primary” — that seemingly interminable period, often stretching out beyond a year, from when the first recognisable presidential candidates emerge and the first actual votes are cast.

With six months still to go until the Iowa caucuses officially start the 2020 campaign, we have only fundraising totals and opinion polls to help winnow down a crowded field of more than 20 Democrats vying for the chance to take on Donald Trump.

For heavily Democrat American Jews, the current winner of the “money primary”, as it is commonly dubbed, is neither Jewish candidate Senator Bernie Sanders nor the frontrunner, former Vice President Joe Biden.

Instead, Jewish donors appear to be lining up behind Pete Buttigieg.

Once seen as a rank outsider, the campaign of Mr Buttigieg, the 37-year-old openly gay mayor of South Bend in Indiana has sparked to life in recent months.

According to The Forward, individual Jews — who make up two per cent of the US population — constituted 5.5 per cent of the donors to Democratic candidates in the first six months of 2019 and contributed more than seven per cent of the money.

“Mayor Pete”, as his supporters call him, headed the pack with donations totalling $1.37 million (£1.13 million), comfortably outpacing Mr Biden’s $1.13 million. Mr Buttigieg has had a little help: among his earliest big endorsers was Steve Grossman, the former chair of the Democratic National Committee and president of the Aipac lobby group.

Led by Mr Sanders — who has released videos calling Gaza an “open air prison” — many in the Democratic field have flaunted their progressive credentials by harshly criticising Israel. Mr Buttigieg has adopted a more nuanced approach which is both fiercely supportive of the Jewish state while vocally critical of the government of Benjamin Netanyahu; it is a position which chimes with the attitude of many American Jews.

Mr Buttigieg, who visited Israel last year with the American Jewish Committee, has blamed Hamas for the plight of Gaza, argued that “we don’t have the right kinds of partners in leadership on the Palestinian side”, and suggested Israelis’ unwillingness to let security threats “dominate [their] consciousness” was a model for Americans. His campaign launch in April was interrupted by pro-Palestinian activists.

Yet he has also labelled Mr Netanyahu’s campaign talk of annexing the West Bank a “provocation” and — in a barely coded hint at cuts to US aid — warned that “a President Buttigieg will … ensure that American taxpayers won’t foot the bill”. The Israeli Prime Minister, the mayor has suggested on other occasions, is “turning away from peace”.

Yet there is none of the over-heated rhetoric into which even justifiable criticism of the Netanyahu government so often slips. Mr Buttigieg’s approach is epitomised by his suggestion that the right approach to an ally whose behaviour one thinks is harmful is to “put your arm around your friend and … try and guide them somewhere else”.

Nor, unlike some other presidential hopefuls, has Mr Buttigieg shied away from criticising members of his own party who have been accused of antisemitism and demonising Israel.

Questioned about Congresswoman Ilhan Omar’s attempt to equate alleged human rights abuses in Israel with Iran, Mr Buttigieg bluntly responded: “People like me get strung up in Iran so the idea that what’s going on is equivalent is just wrong.”

Mr Buttigieg may be showing strength in the “invisible primary” but his path to the presidential nomination is by no means straightforward. Whoever ultimately wins that prize will find many Jewish donors willing to open their chequebooks to help oust Mr Trump.

Few, though, have deeper pockets than megadonor George Soros. Last week he established Democracy PAC, a political action committee from which he will dole out cash in next year’s election.

Mr Soros’ initial outlay of $5.1 million (£4.2 million) represents the single biggest donation so far of the 2020 campaign. The fact that it is more than double the amount he had donated at this stage four years ago suggests thebillionaire philanthropist is gearing up to spend more than he ended up splashing on the Democratic Party in 2016.

In the face of Mr Trump’s huge campaign war chest, however, the Democrats need all the help they can get.