It’s pretty clear that Corbyn has won the re-run, and talk of trying once more next year has faded amid eye-rolling on all sides at the thought of doing it all over again. Instead, the hard-core anti-Corbyn wing has started to talk about a split.

This could take two forms:

• A Parliament-only split. The objective would be to win over more than half the MPs and persuade the Speaker that this meant that the rebels were the real official opposition
• A full SDP Mark II, with or without an alliance with the LibDems.

Given the extent of MP support for the no-confidence letter, it might be thought that either or both of these would gain the support of most Labour MPs. But it won’t, and the sparsity of overt support for it among MPs is a harbinger of what would go wrong. Here’s why.

MPs are a mixture of pragmatists and idealists. They want to do good things, they want to be personally successful. Nothing wrong with that. They’d like the party to win power, since ultimately opposition achieves little. But at a gut level, they want to hold their own seats. Before sneering at that, it should be noted that most MPs really only have one potential job. If they lose it, it’s many years since their previous careers and often impossible to get back into them. A former senior IT manager, I speak from experience.

Under FPTP, MPs for all but the most marginal seats are pretty safe if their party reselects them. Even with the current turmoil, where every news item about Labour is bad and the PM is enjoying a honeymoon, the party is on 28%, enough to hold most seats. But if they split with their party, they can reasonably expect to lose at least half their party vote, putting the vast majority of MPs at risk. This is only remotely attractive if they can be confident that it will attract lots more voters from other quarters. Neither historical precedent (SDP Mark I) nor recent polling suggests that to be likely.

Moreover, the Parliament-only split is the worst of both worlds, since it guarantees deselections without actually providing an alternative electoral vehicle. A full SDP Mark II would require an organisational effort on a scale that is nowhere in sight, with only the scattered remnants of the LibDems to give it any initial national presence.

None of this would matter if MPs expected to be deselected: if you’re going to lose anyway, why not do it in style? But here the other side of the story kicks in: the mood of the membership. Members are irritated by the no-confidence motion and not disposed to tolerate much more of that sort of thing, but they can see why MPs supported it, and suggestions of organised deselection are few and far between.

An MP who merely stops supporting attempts to undermine Corbyn is likely to have a reasonably easy run to reselection, and a fair chance at selection in new seats where a large part comes from an existing seat. The left feels they’re winning, and are in general not in vengeful mood.

Bottom line: expect a few defections to LibDems or Independent, especially in the Lords, but expect the overt attempts to unseat Corbyn before 2020 to fade into resigned acceptance by most MPs. It’s not as though most MPs vehemently disagree with the Corbyn project, parts of which (notably anti-austerity policies) have won the argument – they just think it won’t win under current leadership. The default will be to soldier on quietly, avoiding blame for any defeat. If Labour beats expectations and wins – and nobody in politics ever treats anything as certain or impossible – that’s fine. If it goes badly, then I expect a much more serious leadership contest in 2020, with heavyweight candidates who are currently holding fire.

Nick Palmer was LAB MP for Broxtowe from 1997-2010 and is a long-standing PB contributor