Will Boris Johnson shy away from a contest at the last moment – again?

We will discover our fate as a nation at 2pm on Monday – at the latest. We may find out our fate before then if, as I suspect, Boris Johnson decides not to put his name forward. It would not be the first time that he had withdrawn from a contest in which he risked being humiliated.

In 2016 he stunned the political world by declaring, at the launch of his campaign for the Conservative leadership, that “that person” – he had just listed the qualities needed to be prime minister – “cannot be me”. Michael Gove had scuppered his plan for a clear run at the post-referendum premiership.

If Johnson has not reached the same conclusion before 2pm on Monday, there will be only one number that matters. Has he managed to sign up 100 Tory MPs to support his nomination for the leadership, or not?

If he has, he has a good chance of returning to No 10 as prime minister on Friday next week, after the party members have voted electronically. A good chance, but not a certain one. If, on the other hand, Sir Graham Brady, the chair of the 1922 Committee, announces that he has 99 or fewer names, then Rishi Sunak will almost certainly become prime minister on Monday afternoon.

This is a high-stakes weekend, in which Johnson’s sixth sense for politics will be tested once again. Neither he nor anyone else will know whether he can make it, unless he stays in the contest and finds out. Apart from a proposer and a seconder, the candidates’ supporting nominations will be confidential, known only to Sir Graham (and possibly other members of the 1922 executive).

That means Johnson cannot know whether the MPs who have publicly declared for him so far will actually end up sending Sir Graham the letter or email supporting his nomination. There will be MPs who assure him of their support because they don’t want to explain their private reservations, either to him or, more probably, to their local Conservative associations – some of which are ferociously pro-Boris and may threaten to deselect MPs who don’t support him.

In 2016, Johnson judged that he couldn’t be sure enough of winning, and that losing would hurt his chances of another tilt later. This time, he may decide that the chance has come too soon for him – that Agent Truss has been rather too successful in blowing up the government and making his time in office appear a period of relative calm and sound administration.

If he decides not to run, most of his support will switch to the next available anti-Sunak candidate, which will almost certainly be Penny Mordaunt. She gained 105 votes in the last round of MPs’ voting in July, so there certainly were enough MPs willing to support her in a secret ballot. My guess is that she would come second in what Sir Graham calls an “indicative ballot” – a vote among MPs between just two qualifying candidates. (It is unlikely that there will be three, given that each requires 100 supporters out of the 354 available – there are 357 Tory MPs, but candidates cannot support themselves.)

Mordaunt then has to decide whether to stick or fold. That could depend on two things. If she is a close second to Sunak, and if opinion polls of Tory members suggest she could beat him, she may stay in the contest. The last poll carried out by YouGov on Monday and Tuesday this week put her some way behind Sunak on an open choice: 9 per cent to 23 per cent. But 54 per cent said she would be a “good replacement” for Liz Truss, against 60 per cent saying the same of Sunak.

Otherwise, she may decide to pull out in the name of party unity, in which case the members’ vote would be cancelled – as it was in 2016 when Andrea Leadsom withdrew – and Sunak would head to Buckingham Palace, possibly a bit later on Monday, or on Tuesday morning.

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If Johnson stays in the contest, though, history will arrive at the fork in the road on Monday afternoon. Either he fails to reach the threshold and goes home, or he makes it, setting up a sudden-death contest with his former chancellor that would be as psychologically loaded as the Miliband brothers’ contest 12 years ago.

Despite bold talk from Johnson’s supporters that he would win easily among the members, I am not so sure. That YouGov poll had him scoring only fractionally higher as a “good replacement”, by 63 per cent to 60 per cent, and the markets might take fright again at the prospect of a prime minister who is not good at “abacus economics” – otherwise known as adding up.

Still, the safest assumption of recent history has been that most people involved in politics will make the wrong decisions for themselves and the country, so I had better not predict anything.