In next week’s closely fought US mid-term elections, the outcome of which may decide the fate of Donald Trump’s presidency, Jews could play a pivotal role.

None more so than Jacky Rosen. The former synagogue president was picked by Democrats for the House of Representatives two years ago. Now Ms Rosen is continuing her rapid ascent by attempting to wrest the critical Nevada Senate seat from Republican incumbent Dean Heller.

She is currently running neck-and-neck in the polls in the “swing” state. If Ms Rosen — who the president has christened “Wacky Jacky” despite her reputation as a moderate — fails, the Democrats’ dwindling chances of retaking America’s upper house will likely be buried.

The Republicans hope to maintain their majority by defeating Democrat senators running for re-election in states won by Mr Trump in 2016. Ms Rosen is contesting one of the few Republican-held seats up this year which Hillary Clinton took.

Aside from Mr Heller, Ms Rosen is also running against casino mogul Sheldon Adelson. He is pouring cash into Mr Heller’s campaign chest — part of the $113 million (£87 million) Mr Adelson is spending to help the Republicans hold on to Congress.

His money is matched on the Democrat side by that of another Jewish billionaire: Michael Bloomberg. A one-time Republican, the former New York mayor this month changed his registration from independent to Democrat amid speculation he may be planning to run against Mr Trump in 2020. He recently added $20m to the $80m he has pumped into Democrats congressional campaigns.

Ms Rosen is one of 56 Jewish candidates running for Congress this year.

Forty-one are Democrats and include well-known Senators such as Bernie Sanders in Vermont and California’s Dianne Feinstein. Alongside Ben Cardin in Maryland, they are likely to cruise towards re-election.

In the House of Representatives, 18 Jewish Democrats and two Republicans are hoping to hold their seats. A further 18 Democrats and 13 Republicans are bidding to seize seats from the opposition party.

But it is Jewish voters, not candidates or donors, who may help to decide the outcome of many tight contests this November. Not only do they turn out in higher numbers than most other Americans, but the “kosher vote” is geographically concentrated in key battlegrounds in New York, New Jersey, southern California and southern Florida.

An analysis by The Forward this summer indicated that of those districts rated competitive by the respected Cook Political Report, just under two-thirds had a higher Jewish share of the population than than the median congressional district. These seats — many of them well-educated and suburban — are central to the Democrats’ hopes of winning a majority in the House of Representatives.

Jewish voters could also help to decide the outcome of the knife-edge race for Florida’s Senate seat. Around five per cent of the electorate in this state — which has produced a series of nail-biting results over the past two decades — is Jewish, and the Democrats are desperately trying to cling on to a seat here, where Mr Trump narrowly won in 2016.

As usual, the Jewish vote appears to be leaning heavily towards the Democrats: 74 per cent of Jews, around the same number that voted for Mrs Clinton two years ago, will back it.

Republicans have attempted to eat into the Jewish vote — and fire up their pro-Israel evangelical base — by painting their rivals as anti-Israel. Democrat leaders have pushed back hard, with Nancy Pelosi, who will become Speaker if her party takes the House, last week describing the establishment of Israel as the “greatest political accomplishment of the 20th century”.

The Republican effort may also be stymied by the way the National Republican Congressional Committee has attempted to ape Hungary’s Viktor Orban by introducing the spectre of George Soros into some races, painting Democrats as beholden to the liberal Jewish philanthropist. Jewish Democrat groups have also accused Mr Trump of providing white nationalists with “a home in the Republican Party”.

The focus on Israel by the Republicans also ignores a critical piece of data. Polls show that Jewish voters view domestic issues — including healthcare, the Supreme Court, and social security — as more important than a candidate’s stance on Israel.

Nevada may have only a small Jewish population, but — around the country — many other Jews will cheering “Wacky Jacky” on come 6 November.