What if – horror of horrors – Boris Johnson made a success of Brexit?

So far, I have said that Boris Johnson is likely to be heading for disaster. He seems unlikely to get a Brexit deal through parliament, and parliament is unlikely to allow him to take Britain out of the EU without a deal.

Thus he seems to be heading for a “people against parliament” election, in which he asks the people for a mandate for his Brexit, saying he has been blocked by MPs. Who knows what would happen then, but such an election would take place against the background of Johnson’s failure to deliver the one thing on which he has staked his premiership: leaving by 31 October.

But what if Johnson succeeds? The betting market thinks there is a 64 per cent chance that we will still be in the EU on 1 November. But that means there is a 36 per cent chance that we will be out, so any futurologist worth their salt ought to be able to set out how that might happen.

In the absence of ready-salted futurologists, allow me to try. There are two routes to leaving by the end of October: with a deal, or without one. In the first case, Johnson has to overwhelm either the EU or the UK parliament, or both, to get a deal approved. In the second, he simply has to overcome parliament’s determination to stop him.

In both cases, a large part of Johnson’s strategy is to mobilise public opinion. This weekend’s opinion polls are likely to show a Boris bounce. If that is sustained, it will put pressure on Labour MPs, Tory rebels and EU leaders. As James Forsyth, political editor of The Spectator, says: “His strategy now is that the best way to avoid an election is to show that you would win one.”

Suppose that EU leaders agree to rewrite the protocol on the Irish border. This bit cannot be predicted, but something to do with checks away from the border, which the Irish and the EU have discussed as a possibility in the event of a no-deal Brexit, might allow a form of words.

That wouldn’t be “abolishing the backstop”, as Johnson has demanded, but he could pretend it was. Steve Baker, the Brexiteer Against Brexit who refused to take a “powerless” job working for Michael Gove on no-deal preparations, would not vote for it. But perhaps half of the 28 Eurosceptic Tory MPs who voted against Theresa May’s deal at the third time of asking would do so (at least two of them, Priti Patel and Theresa Villiers, would have to, now that they are ministers).

If Johnson could persuade the DUP’s 10 MPs to join him, he would need only a handful of Labour MPs. Gareth Snell and Sarah Champion have already said that they would now vote for a deal, and the prospect of an election could persuade others.

So it could be done. Maybe not by 31 October. If parliament approved a revised deal, legislation would still be needed to implement the withdrawal agreement. The last time we came round this circle, ministers thought they needed three weeks to get the bill through parliament. But Johnson could live with a short extension of a few weeks if the vote on the principle had been won.

Then there is the prospect, if Johnson cannot get a revised deal, or cannot get a revised deal through parliament, of a no-deal Brexit. That seems harder to achieve. There is a large bloc of Conservative MPs who are totally opposed to such an outcome and who have nothing to lose. Johnson swelled their number by clearing out two-thirds of May’s cabinet.

But it is possible, if Johnson looks as if he would win a general election, that some of them would hold back from the nuclear option of bringing down his government.

A lot might depend in the next three months on Nigel Farage, the leader of the Brexit Party. He is already gearing up to denounce Johnson for betraying Brexit, but at the same time he said on Wednesday: “There is a possibility that an electoral pact could be forged.”

Johnson “could win a landslide in the first past the post system” if he reached an understanding with Farage, as Jonathan Powell, Tony Blair’s former chief of staff, put it today. Powell knows a thing or two about landslides.

And the more likely a no-deal Brexit seems, the more likely leaving with an agreement becomes, in Johnson’s other paradox: that the way to avoid leaving with no deal is to prepare for no deal. If a no-deal Brexit was a real and imminent prospect, many Labour MPs and Tory rebels would rather vote for any deal.

All of which is an attempt to describe how Johnson might succeed in taking us out of the EU. If he does, and especially if he does it by agreement, he will be in a strong position. He could tack back to the liberal centre, from where he won two elections to the London mayoralty. But he wouldn’t be able to do much without a parliamentary majority.

In that scenario, prepare for an election in March.