Is there any chance at all that Labour could lose Edinburgh South?

I've lost count of the number of times over the last year that I've said "if this poll proves to be right, Labour would lose almost all of their Scottish seats to the SNP", with the "almost" referring to the seemingly inevitable fact that Ian Murray will easily hold Edinburgh South for Labour no matter what happens elsewhere.  Last night brought news that the Unite union has voted to "trigger" Murray (ie. to attempt to deselect him as the Labour candidate as punishment for his disloyalty to the party leadership) and that Murray has retorted with all sorts of dark warnings about how replacing him with a "Marxist" could cost their Labour their only safe Scottish seat.  He even suggests that he could help that process along by standing as an independent.

This is almost certainly a bit of a red herring, because reselection attempts very rarely succeed - it's probably intended more as a means of applying indirect pressure on Corbyn-sceptic MPs and encouraging them to toe the line.  It's still pretty likely that Murray will be the Labour candidate at the general election unless he voluntarily walks away.  So the more interesting question is whether there is any chance at all that Labour could lose with Murray as their standard-bearer?

On the face of it, that's a classic QTWTAIN (Question To Which The Answer Is No), because two years ago Murray had a lead of more than 32% over his SNP opponent, which means on a uniform national swing that the SNP would require a highly improbable Scotland-wide lead over Labour of 42% before they could expect to gain Edinburgh South.  But it's worth remembering that in 2015 (the election before last), the SNP came reasonably close to winning the seat with a national lead over Labour of 'only' 26%, and some opinion polls suggest they could be back in that ballpark now.  So if the local contest ends up resembling that of 2015 more than that of 2017, it's not totally impossible that Murray could prove to be vulnerable.

The snag is, though, that what happened in 2017 seemed to decisively change the game and it's hard to imagine that process being reversed.  The decline in the SNP vote in Edinburgh South was actually slightly below the national average, but Labour still built up a formidable advantage by adding 16% to their own vote - completely against the Scotland-wide trend which saw them more or less flatlining.  By contrast, the Tory vote only increased by a trivial 2% locally at a time when it was essentially doubling across Scotland.  It's blindingly obvious that many people who would otherwise have voted Tory lent Murray their vote on a tactical basis to stop the SNP.  And there's little reason to think most of those people would go back to the Tories now, given that Edinburgh is such a solidly Remain city and the Tories are the only major party that is in favour of a Hard Brexit.

But the flipside of the equation is that many people who voted tactically for Murray in 2017 may now be much more preoccupied with stopping Brexit than with stopping a second independence referendum, and will thus no longer have such a laser-like focus on choosing the candidate most likely to beat the SNP.  Is there any reason to suppose that they might be tempted by the Liberal Democrats, rather than the Tories?  Well, yes there is, because you don't have to go too far back in history to find a time when Edinburgh South was a highly competitive Labour-Lib Dem battleground seat.  In fact the Lib Dems came slightly closer to beating Labour in both 2005 and 2010 than the SNP did in 2015.  And the Lib Dems actually held the equivalent Scottish Parliament constituency between 2003 and 2011.

Much depends on whether Remain supporters think that a Labour vote would be an endorsement of Ian Murray's personal anti-Brexit stance, or the Labour leadership's much more convoluted position.  If the latter, we could see a substantial swing to the Lib Dems in Edinburgh South, and that could open up the possibility of either the SNP coming through the middle and taking the seat, or of the Lib Dems winning from nowhere themselves.

I'm not saying that's particularly likely - I would expect Labour to hold on.  But it may be a much more competitive contest than a lot of people are assuming.