A new study indicates that Jewish donors have given far less to American presidential candidate Donald Trump than they gave to the Republican campaign during the last election.

The study, by polling website fivethirtyeight, calculated that Jewish donations to Mr Trump so far make up just eight per cent of what Mitt Romney received during the 2012 race.

The report also estimated that just two per cent of donors to the Republican nominee's campaign were Jewish. Meanwhile, Jewish donors to Mrs Clinton's campaign were at ten times that figure, at 20 per cent.

It has also been reported that Jewish casino mogul Sheldon Adelson would contribute $5m to Mr Trump's campaign, a fraction of the $100m that he pledged earlier this year.

The study indicated Jews had given a far greater proportion of money to the Democrat campaign this time around. Jewish donors have given $95 million to presidential candidates over the course of the extended campaign so far, compared to the $150 million given during the entire 2012 race. Of that money, 84 per cent has gone to Democratic candidates, whereas in the 2012 election the ratio was 70:30 in favour of the Democrats.

The fivethirtyeight report looked at all donations over $200, since that information is publicly available. The names of all the donors were then run through its profiling software.

The study's authors, which added the caveat that their figures were estimates, offered a number of possible reasons why American Jews were not giving to Mr Trump.

These included the number of vocal antisemites supporting the Republican nominee, as well as the perception that Mr Trump has little understanding of Israel or the Middle East.

However, a third reason was Mr Trump's racist remarks and hostility to refugees, which many Jews see as only a step away from the kind of antisemitism that made them flee to America.

Saul Friedlander, the Pulitzer Prize-winning author, was a case in point. The Holocaust historian told the press last Friday he would leave the United States if Mr Trump was elected.

Mr Friedlander was critical of Hillary Clinton, saying: "Unfortunately, she has a tendency to lie about things." However, he saved his most scathing critique for Mr Trump, calling him a "dangerous crazy".