Without electoral reform Labour's future is pretty dire. One way and another the Scots aren't going to avaiable to even the balance, wther as Labour or as SNP. Either Scotland will be independant, or the Tories will have pushed through changes which will neuter their effective. Influence in Westminster.

With electoral reform we'd see a realignment of politics, so that the coalitions would between smaller parties rather than within big parties.

I suspect a rerun of the referendum on the Alternative Vote might produce a very different result. People always talk about that as a massive vote of confidence in FPTP, but in fact the turnout was only 42%, which meant that only one in four people voted that way.

I can't see an SDP type split - but if Corbyn wins there probably will be an organised right-wing Labour group within parliament, an opposition within the opposition. And of course they'll accuse the left of being splitters...