It’s a done deal. Theresa May has bagged the two-thirds Commons support that, under the Fixed-Term Parliaments Act, is needed to call an election before term. The big question is: why did most Labour MPs vote with the government? Given the situation, they should eye an early election with as much relish as badgers do shaving brushes. But no, the ivory-handled bristle has got the brocks crowding the lobby. Less than a quarter of the PLP didn’t back the government: a handful voted against; around fifty abstained.

A parallel question arises about Lib Dem MPs, all whom voted in favour of an early election. They, unlike their Labour counterparts, do at least all want to squelch Brexit, but it's far from obvious that a process likely to end with a three-figure Tory majority is an effective way of achieving this. Remainers’s hopes that May is creating room to ease a softened Brexit through the Commons are probably moonshine; one could argue to similar but opposite effect about a hardened Brexit. Still, the Lib Dems can campaign on a Remain-friendly platform and hope to gain a few seats.

No parallel vision melding principle with electoral salvation exists to comfort Labour MPs. I can think of seven possible explanations for their endorsement of this pointless election. Some may apply to different bits of the PLP; several may apply to the same members at once:

1. delusionally, they think they can win the election;
2. they think it will entrench, harden etc. Brexit;
3. the think it will undermine, soften etc. Brexit;
4. they buy the ‘accelerationist’ view that the worse things get in the short term, the sooner revolution will dawn;
5. they know that doom beckons, but think they have to pretend to think that Labour will win;
6. they embrace doom with the antinomian levity that often greets impending catastrophe;
7. Jeremy Corbyn, delusionally, thinks he can win the election, while other Labour MPs see in it an unexpectedly early chance to get rid of him.

It would be interesting to see how closely the 174 MPs who voted to dissolve Parliament overlap with the 172 who supported a motion of no confidence in Corbyn after the referendum last June. The latter contingent does not include Corbyn himself, though I hesitate to put much past him in the way of political ineptitude. The trouble with this explanation, as applied to the Corbyn-hating wing of the PLP, is that it can work only if a major part of it suffers annihilation at the polls. But the other explanations also have to be consistent with that prospect.

Labour is hobbled by straining to avoid being so Brexity that it alienates its educated metro-liberal fanbase, while not being so Remainy as to alienate its working-class supporters. The latter's support for Brexit may be overstated by those in the party's various leadership circles who think it can't resile on Article 50. But even if it's an imaginary dilemma, the party gives every impression of having impaled itself upon it.

Is this the end of Labour as we know it? Time will tell. Parties do die. Take for instance the American Whig party, which disintegrated in the 1850s over the free soil issue. Differences over whether to extend slavery into the new territories split the Whigs into northern and southern factions. In the north, many ex-Whigs, including Abraham Lincoln, joined the new Republican party. In the south, many joined the nativist Know Nothing party. Labour faces a schism between its nativists and know somethings. The campaign is likely to expose further the tensions between them.