Now we know why Nicola Sturgeon resigned – SNP support has collapsed

It’s just one poll, but we can now see that the bottom had fallen out of Nicola Sturgeon’s world before she announced her resignation on Wednesday. A survey taken by YouGov in Scotland in the six days up to and including the day of her announcement has found that support for the Scottish National Party has slumped, while Labour support has doubled – at the expense also of the Tories and Lib Dems – putting Labour within touching distance of the long-dominant SNP.

Even if other opinion polls don’t show quite such dramatic changes, there is no doubt that something big has happened in Scottish politics. Ever since the referendum on independence nine years ago had the paradoxical effect of energising the losers and dividing the winners, the question has been: around which party will opposition to the independence movement coalesce?

For a while it seemed as if the Conservatives would have to step up and reclaim the Unionist part of their full name. The inherent implausibility of this, given the way anti-Tory sentiment suffuses the tiny world of elite Scottish politics, was briefly overcome by the brilliant and un-Tory leadership of Ruth Davidson, whose party won 13 Scottish seats in the House of Commons in 2017.