On the morning after the UK voted to leave the EU, MPs steeled themselves for an early general election. The event appeared too convulsive for the parliament of 2015 to hold. Fearful of being routed in a snap contest, Labour MPs launched their ill-fated coup against Jeremy Corbyn. A new Conservative prime minister, they assumed, would pounce on their wounded party.

But after entering No.10, Theresa May reaffirmed her campaign pledge not to go to the country (or rather invite MPs to allow her to do so). After the tumultuous 2015 contest and the referendum, her view was that a period of stability was required - a view shared by voters. Many newly-elected Tory MPs, fearful of a Brexit-inspired Ukip or Liberal Democrat surge, supported her on this condition.

“The Prime Minister could not have been clearer,” a senior No.10 source told me. “There won’t be an early election.” Maintaining this pledge was regarded as crucial to promoting May as a “straight-talking” PM. A snap contest would exemplify the gameplaying for which she denounced David Cameron and George Osborne.

There were always Tory MPs who thought this decision imprudent. After the high court’s Article 50 ruling, they are increasing in number. Brexiters such as Iain Duncan Smith and Dominic Raab have told May to prepare for an early contest if parliament obstructs her negotiating terms.

Downing Street has insisted this morning that nothing has changed. "We've been very clear: there is no requirement for a general election,” a spokesperson said. But if, as seems likely, the government loses its appeal against the court ruling, the facts will have changed. Parliament will have a chance to prevent “hard Brexit”: defined as leaving the single market to regain control of immigration. The government’s working majority of 16 is too slight for May to be confident of prevailing on this point.

This is far from the only reason for the PM to alter her view (though the likelihood remains that she will not). The Tories enjoy an average poll lead of 15 points, an advantage that would deliver a landslide victory. Labour is performing at the worst level of any post-1945 opposition and is led by the still-more unpopular Jeremy Corbyn (the latest YouGov poll has him 31 points behind May and 20 points behind “don’t know”).

Neither the leaderless Ukip nor the Lib Dems have enjoyed the surge that some predicted. In the by-election in Richmond, which voted 69-31 to Remain, Brexiter Zac Goldsmith enjoys a commanding 23-point lead.

The economy has far outperformed expectations, avoiding the immediate recession that many Remainers forecast. The pound’s sharp depreciation will bring higher inflation. But that is merely an argument for going to the country before voters feel the squeeze.

It was said that an early election would force May to reveal her negotiating hand. But MPs will likely ensure she does anyway. With greater definition would come greater division. There is no guarantee, however, that a 2020 general election would minimise the Tory split. Indeed, if May accepts transitional membership of the single market (necessitating EU budget contributions and free movement) while a free trade agreement is negotiated, the divisions will be intensified.

Unlike her predecessors, the Prime Minister faces the hurdle of the Fixed-Term Parliaments Act (under which the next election will be on 7 May 2020). Yet it is not an insurmountable one. The legislation can be suspended with the backing of two-thirds of MPs, or through a vote of no confidence in the government. Alternatively, the act could simply be repealed or amended. Labour and the Liberal Democrats, who have demanded an early election, would struggle to resist May if she called their bluff. The Tories would miss the chance to introduce the boundary changes (due in 2018), which would gift them another 30 seats. But in view of their current poll rating, this is a small sacrifice to make. It is far from certain, in any case, that parliament will pass the legislation.

The longer May waits,, the greater the risk of a recession (be it Brexit-related or not) and of an opposition recovery (some of Corbyn’s own allies do not expect him to last till 2020). With her own mandate, she would be empowered to dismiss recalcitrant MPs and peers.

Prime Ministers are rarely stronger than when they first enter office. Some Tories believe May has already missed her best chance to call an early general election. She should not, they say, miss the second-best.