This may seem ridiculous, but leaving the EU might not trigger the apocalypse. What then for UK politics?

I wasn’t intending to write about Brexit, but there is one possible outcome that seems to have been left out of recent commentary.

This may seem ridiculous, but what if leaving the EU is a success? Just suppose, for the sake of argument, it turns out all right – not great, because that really would be fanciful, but all right.

Listening to David Davis, the Brexit Secretary, this week brought home the complexity of what he is attempting. He gave evidence to the select committee on Wednesday and then spent as long in the Commons chamber the next day answering questions about his answers.

He wants to agree and ratify one or more treaties on three things at once: the terms of exit, the long-term relationship and the transition period in between. All by 29 March 2019. People who know about trade negotiations say this is impossible. Davis and the Prime Minister say it is different because we start off in the single market, so it is not like negotiating to open up trade between previously divergent economies.

I don’t know who is right, but I suspect that, if the EU side decides that it doesn’t want us to leave without an agreement, it would be possible to sign a skeleton treaty – one that leaves a lot of details to be negotiated later, during the transition or “implementation” period. The “ifs” are important, but if that is what the EU27 decide, and if agreement is reached, and if it is ratified, then we might leave the EU without triggering the apocalypse and the British people might look up briefly from Come Bake With Me and wonder what all the fuss had been about.

Admittedly, that means a Brexit department with a high turnover of ministers and officials has to negotiate a deal, and the Walloon regional parliament in Belgium (which held up the Canadian trade deal) has to approve it, but it could happen. One parliament that won’t block it is the Westminster one unless, as I have argued before, there is a bigger shift in public opinion against Brexit than anyone expects.

So let us imagine that Theresa May does a deal. Nothing much would change on 30 March 2019, except that EU citizens would have to register if they move here, British MEPs would be ejected from the European Parliament and we would no longer be an EU member state. The difficult bit – the cliff edge, although now it would be more like a haha – would have been postponed until the end of the transition period in 2021. After that, we would have agreed to pay for access to the single market, either through tariffs or an annual subscription.

That would mean that nothing much happened before the next election in 2022. Economists would still be saying that Brexit was making us poorer. And it would be, but most of those effects would not be felt for years.

Yet the whole of politics would turn on a sixpence. Once we have left the EU everything changes. The “stop Brexit” movement would transform and shrink into a “rejoin the EU” movement. Theresa May would still be unpopular – that is, the normal condition for most prime ministers most of the time – but people would be pointing to new similarities with Gordon Brown. From the depths plumbed after the election that never was, Brown earned enough grudging respect for his handling of the financial crisis to deny the Conservatives a majority in the 2010 election.

For May, the humiliation of the election she wished had never been would be partly offset by the delivery of Brexit. Leave voters would be unhappy about the absence of a Brexit dividend for the NHS, but they might have some grudging respect for a leader who had acted on the will of (just enough of) the people.

At the very least, it would change the assumption that May could not possibly lead the Conservatives into the next election. As Matt Chorley pointed out in The Times recently (“Theresa clings on, obviously”), prime ministers tend not to leave office voluntarily, so if they want her out they will have to come and get her out. Everything depends on the balance of forces between her and Jeremy Corbyn. If she looks as if she would lose the election for the Tories, they will dispose of her. But a non-disastrous Brexit would at least give her a chance.

The odds are still stacked against her. The pressures for more public spending are intense, not just in the NHS but in housing, universal credit, schools and student finance. They are not going to be eased by next month’s Budget, and the economy can’t be counted on to deliver windfall revenues over the next few years, regardless of Brexit.

The other effect of Brexit might be to unite the Labour Party. Once we are out, Corbyn wouldn’t need to triangulate between Labour leavers and remainers any more, whereas the Cabinet would still be split between huggers and divergers – those who want to hug the EU close and those who want to separate our economy more from the gravitational pull of the eurozone.

So I doubt that even a non-disastrous Brexit could save Theresa May in the end, but it would save her place in history.

After a week in which journalists have speculated that she wants to give up, I think it more likely that she and Philip, her husband and adviser, hope to turn things round. If she quit now, she would be remembered as the prime minister who lost her majority in a needless election and who gave up in the face of a challenging task. She must want to be remembered as the prime minister who took us out of the EU, as was the mandate of the people.