Back in April, I speculated on the fate of the SNP following a No vote on Scottish independence:

“It’s difficult to see a defeated Alex Salmond staying on as party leader (though he could continue as Scottish first minister). That would leave Nicola Sturgeon or some other successor to negotiate an enhanced form of Scottish devolution that is bound to follow the defeat of Scottish independence.

“Certainly, there’s no foreseeable prospect of the SNP losing its status as the main rival to Labour north of the border. It might even pick up a few extra seats at the next general election – making it a potential coalition partner in the event of a hung parliament.

“After the next Scottish parliamentary elections, it’s possible that the post-Salmond SNP will find itself out of power in Edinburgh, but in government down south!”

The weakest element in this set of predictions is the notion that the SNP might loose power in Holyrood next time round. Given the Labour weaknesses exposed in the referendum campaign, I’d now be very surprised if this happened.

As for the SNP picking up a “few extra” Westminster seats in 2015, Peter Kellner of YouGov, thinks it could be rather more than that:

“The London-based parties have now offered Edinburgh more powers. These will need legislation in the new Parliament after next May. This gives the SNP a perfect election platform: ‘Vote SNP to force London to keep its promises’.

“In 2010, Labour won 41 seats in Scotland with 42% of the vote, while the SNP won six with just 20%. In the 2011 Holyrood elections, the SNP outpolled Labour by 45% to 32%; in this year’s European Parliament elections, the SNP outpolled Labour by 29-26%… Parity in votes between SNP and Labour next May now looks perfectly possible. This could give the SNP up to 20 more seats, mainly at Labour’s expense.”

Elsewhere in his fascinating analysis, Kellner argues that a Westminster breakthrough for UKIP is also within the bounds of possibility:

“Earlier this year, I thought Ukip would probably win no seats next year. I can now envisage them winning up to ten: Carswell and Reckless for a start, with Nigel Farage probably winning in Thanet South, Diane James possibly winning in Eastleigh, where she came close in last year’s by-election, and half a dozen other seats along England’s east coast between the Humber and the Channel.”

At the same time, the Lib Dems could easily lose around half their seats, which (together with the SNP and UKIP breakthroughs) would add a whole new layer of complexity to the coalition politics of the near future:

“Imagine a dead heat, with Labour and the Tories winning 280 seats each. Adding in the Lib Dems would take the prospective coalition total to just 310, still 16 seats short of the 326 needed for an overall majority. Forming an effective government in Westminster would become a nightmare.”

With these numbers, the Conservatives would need to form a coalition not only with the Lib Dems, but also UKIP and (presumably) the DUP. Good luck with that one.

For Labour, a centre-left coalition with the Lib Dems and the SNP looks more manageable, but in the absence of English home rule that would mean Scottish Nationalists deciding who ruled in England. Indeed, there’s nothing in our present constitutional arrangements to stop SNP ministers from serving in the UK government – even in positions with direct responsibility for entirely devolved matters (devolved, that is, to Scotland).

The SNP might regard this as poetic justice for all the years in which Conservative ministers occupied the Scottish Office, despite the small and diminishing number of Tory MPs north of the border. However, that was in the pre-devolutionary era.

Now that devolution to the smaller home nations is all-set to go much further, the idea of a Lab-Lib-SNP coalition government in Westminster, controlling English domestic policy with Scottish and Welsh votes, becomes utterly absurd, though mathematically plausible.