This should have been Boris’s worst week, but it is Labour facing a calamity

The Prime Minister may still come to regret his election gamble if the Liberal Democrats surge

The last winter general election did not end well for the Conservative prime minister who called it. Edward Heath went to the country in February 1974 with a majority of 30 and a marginal lead in the opinion polls only to lose power to Labour in a hung parliament. In the midst of an economic crisis and with the miners about to go on strike, he called the election to answer the question: “Who governs?” The answer came back: “Not you, Ted.” He tried to forge a coalition with the Liberals but was rebuffed.

In truth, snap elections – those held outside the usual parliamentary timetable to deal with a seemingly intractable issue – have rarely worked to the advantage of the incumbent.

The last election in December is a case in point. In 1923, the new Tory prime minister, Stanley Baldwin, had a majority that would have lasted four or five years but picked a fight with the Liberals and some in his own party over tariff reform and sought his own mandate. He lost his majority and, within a few weeks, Ramsay Macdonald was in No 10 at the head of the first ever Labour administration.

But we do not need to go back that far to see the perils of a snap election, only to 2017 when Theresa May descended from her Welsh mountain top to surprise everyone, not least her own Cabinet, by calling for a poll she had hitherto resisted.

Sir Anthony Seldon’s new book on Mrs May’s premiership has reinforced the conventional narrative about that campaign and how another PM in possession of a Commons majority and an opinion poll lead managed to lose both through a combination of obduracy, sullenness and an inability to communicate anything other than platitudes.

Sir Anthony says that the campaign “cruelly exposed her unusually inflexible and introverted character”. And so it did. But the uncomfortable fact that Mrs May’s detractors tend to brush aside is that she won a bigger share of the vote than David Cameron did in 2015. In fact, she won a higher proportion of the electorate than Tony Blair did in 2001 when he racked up a Commons majority of almost 170.

The 2017 election was not a calamitous meltdown for the Tories. What was unexpected was the performance of the Labour Party. Everyone thought the Tories would win a massive majority because they were running at 48 per cent in the opinion polls while Labour was on 24 per cent. Although the Tory vote fell back during the woeful campaign, it still ended at a historically high level. Boris would kill to get a 43 per cent share next month.

His hopes are based on the opposition vote splitting while the Brexit Party eats into Jeremy Corbyn’s base in the North and denies him victory in Midlands marginals, as happened in 2015 with Ukip. The big shock in 2017 was that Labour’s vote rose so much. Analysts said a

“youthquake” propelled them to unexpected heights but while Labour was popular among young people it failed to get them into the voting booth.

The British Election Study for 2017 concluded that Labour principally picked up votes from other parties.

Nearly two thirds of 2015 Green voters switched to Mr Corbyn and half of all Remain voters backed Labour because they saw the party as the best obstacle to Brexit despite its manifesto commitment to implement the referendum result.

This is highly unlikely to happen again. Mr Corbyn can only pull off the People’s Champion trick once and he will not get those hopeful Remainer votes this time. In fact, the bigger danger for Boris is that Labour’s vote collapses and Remainers swing behind the Lib Dems in large numbers in Conservative seats because they no longer fear a Corbyn-led government.

This is the calculation behind Jo Swinson’s gamble to give Boris an election that he would otherwise not have been able to achieve.

Indeed, Tory strategists had started to fear he would be trapped for months in Downing Street, unable to do anything much at all before the cavalry arrived at the weekend in the unlikely form of the Lib Dems and the SNP to offer him an election lifeline.

You have to hand it to Boris. This should be the low point of his brief premiership yet he has managed to turn it into a minor triumph through a combination of sheer brass neck tactics, plenty of luck and quick-footed parliamentary manoeuvring. He said we would be leaving the EU tomorrow and we aren’t. He said he would not seek an extension to the UK’S membership and he did. Pilloried in the courts and defeated in Parliament, he has none the less secured a new deal with the EU against the odds and now has an election, though he might have been better off seeking one before he was trapped by the Benn Act.

Nonetheless, he has been able to depict Mr Corbyn as running scared, spluttering and blustering in the Commons as he tried to justify his pusillanimity. The Labour leader was snookered; and his only way out was to cave in and back the election.

However, once the campaign is under way, nothing can be taken for granted. Two of the last three elections resulted in a hung parliament and David Cameron only squeaked home in 2015. Mr Corbyn’s support two years ago was artificially inflated by Remain voters who will now look elsewhere. Last time, Labour made the election about domestic policy but this is about Brexit. Why would anyone on either side of the argument vote for a party whose policy is so confused?

The bookies have made Mr Johnson the odds-on favourite to win a majority but they said the same about Mrs May in 2017. The Tories elected him leader anticipating an early election because he is the complete opposite of his predecessor, an accomplished campaigner who earned his spurs in London, twice defeating Ken Livingstone, a far more charismatic Left-winger than Mr Corbyn.

But the threat this time will come from the Lib Dems. Mr Johnson will attack them as neither Liberal nor democratic but they have a clear policy on Brexit: they want to reverse it. They are not far behind Labour in the polls. If they can edge ahead during the campaign and aim to hold the balance of power in another hung parliament, Boris may come to rue his pre-christmas gamble.