As you may have seen on social media, there was a post on the LSE politics blog yesterday arguing that the notion of a "Corbyn bounce" in Scotland at the general election is a "myth" and a "mirage", and that the SNP should not be sidetracked into strategies to fend off Labour when the Tories are the real enemy. It would be comforting to agree with that, and to tell ourselves there is only one unionist party worth worrying about, but I do think the conclusion is wrong. The main flaw of the blogpost is that it treats the results of the 2015 and 2017 general elections as if they are the only pieces of information available to us. When you look at it that way, it does appear superficially that the entire drop in the SNP vote can be explained by a natural 'correction' after the freakish result of 2015, and that the very small revival in the Labour vote (from 24% to 27%) was an inevitable side-effect of that readjustment, rather than being caused by the phenomenon that generated a much bigger Labour surge in England.
However, if you widen your gaze to take account of opinion poll evidence (and indeed the Holyrood election of last year), the picture suddenly looks very different. There is overwhelming evidence that Labour's true recovery in Scotland was not from the low of 24% recorded in 2015, but from the much worse position that the party slumped to after that election. Survation, who proved to be the most accurate pollster, had Scottish Labour languishing at just 18% as recently as mid-April, but by the end of the campaign that had jumped to 29%. Other firms showed a similar trend (even if the exact figures were very different). That sort of big shift is much more in line with the Corbyn surge that occurred in England, and given that it happened at exactly the same time, it's not unreasonable to suppose that it probably happened for much the same reason. It can't really be explained by the correction in the SNP's vote share, because the SNP had dropped to the low 40s (and the Tories had risen to the high 20s) before the Labour surge even started. It looks much more likely that the SNP suffered a drop from an unsustainable high, and then suffered a further small drop as a direct result of voters switching to Labour because of enthusiasm for the Corbyn project.
Even though the premise of the LSE blogpost is wrong, I do think it's correct to argue that the SNP shouldn't head off on a radical left wild goose chase to try to deal with the Corbyn threat. If you're losing voters who are inspired by the prospect of a radical left government at Westminster, you can hardly counter that by offering a radical left opposition at Westminster (and an opposition with third-party status at that). You can only compete by putting forward an alternative inspiring vision that Corbyn can't/won't offer - and that means a much greater focus on independence than we saw in the recent campaign.
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Elsewhere in the LSE blogpost, a reasonable point is made about the SNP's "heroic" determination to conflate support for independence with support for remaining within the European Union, which may have cost the party votes from Brexit supporters. That factor may also go a long way towards explaining the Tories' seemingly puzzling failure to defeat the SNP in places like Perth & North Perthshire and Edinburgh South-West - both constituencies that voted Remain by a much more emphatic margin than the rural north-east did.
But this is not just a dilemma for the SNP. Could the Scottish Tory surge be a similar phenomenon to the SNP surge of 2015? In other words, was it partly caused by temporarily energised Brexit supporters who were determined to reinforce their vote from the referendum last year? If so, the Scottish Tories are very likely to suffer their own natural 'correction' at the next general election (as long as it doesn't take place in the near future). Those new north-east Tory MPs, especially the ones with the narrowest majorities, probably shouldn't get too comfy in their seats.