Is a vote for the SNP in practice a vote for Corbyn?

Nicola Sturgeon says she wants to form a “progressive alliance” after the election to evict Boris Johnson from 10 Downing Street - which in practice means an arrangement with Labour to make Jeremy Corbyn prime minister (this could be a formal coalition though Sturgeon told me she would prefer a less constraining arrangement).

And she also says that in the event parliament is hung, on 13 December, there is literally no chance she would sustain the Tories in power - even if Johnson did a dramatic vote face and agreed she could have her cherished referendum on independence for Scotland.

Which means that a vote for the SNP can be seen as a vote for Corbyn to become PM.

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And it also probably means that a vote for Labour is - whatever Corbyn’s constructive ambiguity on IndyRef2, and Scottish Labour’s implacable opposition to IndyRef2 - a vote to accelerate a second referendum on Scottish independence.

How this will all play out at the ballot box in a few weeks is unclear.

It is plainly an attempt to squeeze Scottish Labour till the pips don’t just squeak but scream in agony - because Labour supporters who want Scotland to stay part of the UK will feel under huge pressure to vote for the Lib Dems or the Tories.

For what it is worth, senior SNP figures tell me they see the battle in Scotland as effectively a contest between them and the Tories.

Less clear are consequences for the Tories and Labour in England.

Johnson will be thrilled that Sturgeon is reinforcing his charge that Labour is the party of two referendums, for the EU and Scotland.

But it is not obvious that this as devastating a charge against Corbyn and Labour as Johnson thinks.

There are plenty of English Remainers who may see Sturgeon as a moderating influence on a Corbyn government and as a powerful ally and campaigner if they secure from Corbyn the EU referendum they crave.

And as I said to Sturgeon, if the UK were to vote next year to remain in the EU, that could significantly reduce the hunger of Scots to separate from the UK. A Corbyn/SNP government alliance may not in practice be more of a spur to the disintegration of the UK than the formation of a new Johnson administration from which a majority of Scots would feel alienated.

The view here in Edinburgh is not of UK politics as the equivalent of simple and predictable Newtonian Physics. There are too many variables: this is chaos theory made real.