I was a bit disconcerted last night when I heard that Labour had "gained a seat from the SNP" in a local by-election, but as is so often the case with STV by-elections, things weren't quite as they seemed. The SNP were "defending" the seat in the spite of having lost the popular vote in the ward last time around, and they actually moved ahead of Labour to win the popular vote yesterday. They then perversely lost the seat anyway due to Tory voters breaking almost four-to-one in favour of Labour on lower preferences. So, other than the fact that the "Auld Alliance" from 2014 is alive and well, and the fact that Irvine West will now have to put up with a Labour councillor rather than Nicola Sturgeon's dad, the nominal "Labour gain" is of very little significance - the underlying trend is still the familiar one of Labour support draining away in former heartland areas.
Irvine West by-election result (11th August) :
SNP 37.5% (+0.7)
Labour 33.1% (-7.1)
Conservatives 20.6% (+8.6)
Socialist Labour 4.2% (+2.6)
Greens 3.0% (n/a)
Liberal Democrats 1.5% (-3.2)
Swing from Labour to SNP = 3.9%
Much the same trend was seen in yesterday's other by-election in Renfrew South and Gallowhill - except here, the SNP built up enough of a first preference lead to actually gain the seat from Labour, even allowing for the "Tories for Corbyn" factor.
Renfrew South & Gallowhill by-election result (11th August) :
SNP 47.8% (+6.9)
Labour 36.9% (-8.5)
Conservatives 13.4% (+9.1)
Liberal Democrats 1.9% (+0.1)
Swing from Labour to SNP = 7.7%
So the average pro-SNP swing yesterday was around 5.8%, and of course that's measured from the 2012 result, when the SNP were already slightly ahead of Labour nationally. Certainly there's nothing in these results that would call into question the sense of inevitability about what will happen next May - Labour remain firmly on course to lose their remaining local government strongholds, including most obviously Glasgow, which will be a landmark moment on a par (almost) with the fall of Byzantium.