The spectacular own-goal that was Theresa May’s decision to call a general election two years ago almost produced a Jeremy Corbyn premiership.

But, despite her multiple flaws, the Prime Minister had one major asset. 

However low her ratings sank, she remained just popular enough in head-to-head match-ups to outpoll the Labour leader. 

Mrs May thus appears to have been the Jewish community’s unloved and battered insurance policy against the antisemitic hard left.

With her resignation, that insurance policy has now expired. 

At present, her most likely successor, Boris Johnson, does not appear quite such a sure bet. 

It’s true that Tony Blair – who knows a thing or two about winning elections – last month declared that he was sure that, given the choice between Corbyn-style socialism and the kind of right-wing populism in which Johnson now trades, the latter would triumph. 

Many Labour party members seem to agree: a recent poll of readers of the Labour List website suggested that most viewed the former Foreign Secretary as their most potent rival. 

And a further poll, commissioned last week by Politico, suggested that, of all the potential candidates for the Tory leadership, Mr Johnson had the best chance of holding together the coalition which – albeit narrowly – delivered the Conservatives victory two years ago.

But others aren’t so sure. Matthew d’Ancona, a journalist close to David Cameron, last week assessed that it was an “epic self-delusion” on the part of the Tory party to assume Mr Johnson could beat the Labour leader. 

“After the briefest of honeymoons,” he wrote, “the voters would quickly start to wonder how this spectacularly incompetent braggart, with a Churchill complex but no Commons majority, had ended up in Downing Street in the first place.” 

A poll last autumn – admittedly an age ago in the current volatile state of British politics – likewise suggested that voters would opt for Mr Corbyn over the former Foreign Secretary. 

Moreover, deep-seated antipathy towards Mr Johnson among many voters might help glue back together the Labour vote which rows about the leadership’s Brexit policy is threatening to tear asunder.

There is a deep irony here. In 2008, it was Mr Johnson who saved London’s Jews from another term of Ken Livingstone as their mayor. Four years later, even as the national tide flowed against the Tories, he was popular enough among non-Tories to frustrate Mr Livingstone’s dreams of a comeback. 

Mr Johnson’s unique appeal – beloved of the Tory grassroots even while cosmopolitan London returned him to City Hall – was obliterated by his decision to lead the Leave campaign in 2016. It’s hard to see, given the country’s current polarisation, how he could rebuild it. 

If Mr Johnson – or another hardline Brexiteer – makes it to No 10, that might stop the Tories haemorrhaging votes to Nigel Farage, but at the cost of centrist voters who have backed the Conservatives over the past decade fleeing to the revived Liberal Democrats.

The results of both the local elections and the European elections underline that British politics is in a state of flux: both Labour and the Tories are deeply unpopular and May’s departure won’t suddenly cure the Conservatives’ ills. 

Might a Johnson premiership – and the risk of Mr Corbyn in Downing Street – force some form of political realignment in which the country’s vital centre inside and outside parliament coalesces around some new force?

Possibly. But the greater danger is that, amid chaos and a splintered vote, Mr Corbyn sneaks into office even as two-thirds of the country or more votes against him.