If Boris Johnson succeeds in taking Britain out of the EU, Jeremy Corbyn will be pleased. The Labour leader has to pretend he wants an election now, but he must dread the prospect.

He does not really want Brexit to be postponed and to have to fight an election campaign explaining that he has no view on whether we should leave or remain. “Get Brexit done” would be a strong message for the Tories, especially if the Labour counter-offer is “whatevs”.

I do not know how likely a deal is, but I observe that the interests of the parties are aligned. There is a majority for a deal in the House of Commons, including the Democratic Unionist Party. And the EU27 want a deal, including the Irish government. If there is something that satisfies both Arlene Foster and Leo Varadkar, it will happen.

It may involve Northern Ireland being in two customs areas at once, which sounds a bit like the “new customs partnership” once proposed by Theresa May, which Johnson, as foreign secretary, described as a “crazy system”. But perhaps it was just ahead of its time.

Anyway, it is possible that a deal may be passed by parliament next Saturday, so it is worth thinking about what would happen next. First, Johnson and the Conservative Party would get a boost in the opinion polls.

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The Brexit Party is at 12 per cent at the moment, and if we left the EU you could expect a large chunk of that support to switch to the Tories. No doubt Nigel Farage would complain about the wrong sort of Brexit and betrayal, treachery, surrender, vassalage – all that violent language people are not supposed to use.

But I think most of his voters would say “job done” and wait for the betrayal later. And if opinion polls suggest Johnson is on course for a majority of 180 seats, I suspect Labour MPs, never as keen as their leader on an election, might decide they had more important things to do than give the prime minister the two-thirds vote he needs.

I suspect Corbyn will have mixed feelings, but relief will probably be uppermost if parliament refuses to vote for an early election. I think he and his inner team are confident they can repeat some of the magic of 2017, but immediately after a triumph for Johnson might not be the best time to try it.

Better, Corbyn might think, to show strategic patience, wait for Johnson’s Brexit euphoria to pass, and harry a minority government on the NHS, schools and crime. The Conservatives and DUP would still be seven MPs short of a majority – even if 15 of the Gaukward Squad (the Tory rebels, including David Gauke) vote for the Brexit deal and have the Tory whip restored.

If a Brexit deal would be good for Johnson, mixed for Corbyn and bad for Farage, it would be disastrous for Jo Swinson. She has bet the mortgage on stopping Brexit, which has lifted the Liberal Democrats in the opinion polls and prompted the defection to her ranks of seven MPs. But if we leave the EU what then does the party stand for?

Many thoughtful members were worried about this at the party conference in Bournemouth last month. “We would have to become the party of Rejoin,” they said in private, fretting that this would appeal to a tiny proportion of the voters, and that the party didn’t have distinctive policies on anything else.

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If we leave the EU at the end of this month – or possibly a few weeks later if extra time is needed for the legal formalities – politics is going to change utterly. The great cleavage between Leave and Remain that has reshaped parties will suddenly lessen in intensity.

The two parties on the far wings of that divide, the Brexit Party and the Lib Dems, will shrink. The competition between Conservatives and Labour over tax and public spending will snap back to familiar territory – although, as a result of Brexit, Tory support is more working class and Labour support more middle class than it has ever been.

Our relations with the EU will continue to be important, and in the endless negotiations that will follow our departure the Tories will seek more independence, while Labour will want closer ties.