And this is really tearing Labour apart, to the point where MPs are plotting a coup if he wins.
And the one thing that's _really_ obvious to me is that this is all the fault of the electoral system. If we had a proportionate electoral system then at some point either the centre ground would have split off (presumably in the 90s) or the left-wing would have split off (presumably in the 2000s), and we'd have two reasonably sized "Left of the Conservatives" parties, which would give voters a choice of who they supported in each election, and where they wanted the government to go.
As it is, we're stuck with parties constantly at war with each other - and frequently at war with their base, as most of the MPs want a party that wins elections, and the base want a party that represents their views.
Original post on Dreamwidth - there are comments there.