Last week's YouGov poll was the first relatively good poll for the SNP for several months, although the reporting of it was accompanied by a flat statement from John Curtice that the swing back to the SNP wouldn't be enough for them to hold the Rutherglen & Hamilton West constituency in the forthcoming by-election. Although that's true, it doesn't tell the full story.
The 11-point national lead for the SNP in the YouGov poll suggests there has been approximately a 7.5 point swing from SNP to Labour since the 2019 general election. If that swing is applied to the Rutherglen seat, it's enough to put Labour ahead, but only by around five points. In other words, if the YouGov poll is exactly right, Labour should be regarded as favourites in Rutherglen, but the contest should also be regarded as competitive.
Now in practice I would expect Labour to win the by-election by more than five points. The YouGov poll may well flatter the SNP a bit, because it's out of line with what other polls have shown recently. And there are difficult local circumstances for the SNP - they stupidly participated in the prolonged demonisation of their former MP Margaret Ferrier, thus grotesquely allowing sleaze-ridden Labour to present themselves as a new broom. Labour's status as an opposition party in both Holyrood and Westminster makes it a lot simpler for them to attract protest votes. And there have been other miscellaneous problems for the SNP such as the paid leafleters story.
But nevertheless, the YouGov poll is the closest thing the SNP have had to a genuine glimmer of hope since the sorry saga of this by-election started.