MPs had the chance to take back control of Brexit – wresting this tortured process from a weak, flailing and moribund government – and they ducked it. Sure, it was by the narrowest of margins, losing by just two votes, 312 to 314, but MPs passed up the opportunity to take charge and say, at long last, what kind of Brexit they want. They preferred instead to grant Theresa May yet another lifeline for her own deal – which, incredibly, will come back for a third meaningful vote on Tuesday.

The lever that was offered to MPs, by which they might have finally got a grip on the Brexit crisis, was a proposal from Hilary Benn that would have seen a series of votes allowing MPs to indicate their preferred Brexit plan – whether that be Norway plus or a second referendum or every shade in between. No longer would May retain the initiative, with the power to confine MPs to a single, binary choice: my way or the highway.

Had it gone through, it would have confirmed what the rest of this week had already suggested: that power is haemorrhaging away from this prime minister, that this government is in office but not in power, that it is parliament rather than Downing Street that now calls the shots. But, by a whisker, May’s administration clung on, the party whip having lost not all of its sting. In fact, it was six Brexiter Labour MPs who saved May from what would have been further humiliation, voting against their colleague Benn and giving her a stay of execution.

It now means the prime minister can stage next Tuesday’s vote the way she wants it: as an ultimatum to the ultras of the European Research Group and the Democratic Unionist party. Thanks to another, much more comfortable vote this evening, approving in principle an extension of article 50, those intransigents will now face a sharp dilemma. The ERG and DUP either swallow their objections and vote for May’s deal, or they face the prospect of a long delay to Brexit – perhaps for the best part of two years. Given the mayhem on show these past few days, who would bet what might happen to their precious Brexit project between now and 2021? They might lose it altogether.

That is the stark, binary choice May has always wanted to press upon the Brexiters, and the defeat of the Benn amendment allows her to do it. She – and her plan – get to live till Tuesday.

Some of her colleagues want to say that something else momentous was decided this evening: the rejection of a second referendum. It’s true that the Commons delivered a crushing rejection of that idea. True too that the margin of defeat will be used to taunt and torment people’s vote campaigners for days, maybe weeks, to come: “Your precious second referendum was rejected even more decisively than May’s plan back in January!” they’ll say.

But that taunt will only have a tenuous relationship to the truth, because this was hardly a real test of the idea. Labour abstained on the proposal, while even the official People’s Vote campaign said now was not the right time to push it. It was tabled by Sarah Wollaston of the Independent Group, perhaps to embarrass Labour and highlight the party’s lukewarm support for the campaign, but it was hardly smart tactics: it now allows opponents to claim there is no support in the Commons for a second vote when, in fact, there’s much more than tonight’s vote suggests. It was a misstep by the remain camp, which has demonstrated that it is far from united, and riven with tensions of its own.

One almost-clear thing does emerge from tonight’s vote. That date you had in your diary, circled in joyful red or in sombre black depending on your point of view – you can now uncircle it. Whatever else happens, it is all but certain that Britain will not be leaving the European Union on 29 March.

That’s because MPs voted by 413 votes to 202 to request an extension of article 50. I say request, because it’s up to the 27 EU nations that Britain will soon leave behind to give their blessing to a delay. Still, given that they also don’t want a no-deal crash-out in 15 days’ time, it’s a good bet they will say yes. Even if May works a Lazarus miracle on Tuesday, winning approval for her Brexit deal buried twice over by successive Commons defeats, she will still need an extension into the summer to get all the technical stuff through, and that’s even before talks get started on the future relationship. So doomsday – or day of liberation, if that’s how you see it – is no longer scheduled for 29 March. This Brexit saga will go on and on.

• Jonathan Freedland is a Guardian columnist