TNS have today published their third full-scale Scottish poll since the referendum...
Scottish voting intentions for the May 2015 UK general election (TNS, 18th March - 8th April) :
SNP 52% (+6)
Labour 24% (-6)
Conservatives 13% (-1)
Liberal Democrats 6% (+3)
Greens 3% (-1)
UKIP are not listed because they're literally on zero (there were two respondents interested in a Farage à trois, but they were rounded down to zero).
These figures mean that TNS are suggesting an absolutely astonishing trend over the last few months. Their first post-referendum poll in January/early February produced an SNP lead of 'only' 10%, which made it look as if they were going to slot in as one of the most Labour-friendly pollsters. A second poll not long afterwards saw the lead increase to 16%, which was pretty much in line with most online pollsters. Now, in one fell swoop, the lead has reached 28% - which completes a rapid transformation for TNS and leaves them as one of the two most SNP-friendly firms. (The other is Ipsos-Mori, which also showed a position of SNP 52%, Labour 24% in their most recent poll - but that was way back in January.)
Now it's true that last week's YouGov poll also showed the SNP lead reach a record level, so it would be wrong to instantly dismiss the TNS poll as an obvious outlier. It now seems much more likely that there has been further movement to the SNP at some point over the last few weeks. But the sheer scale of the swing suggested by TNS over such a relatively short period of time is not something that has been recorded by any other firm so far, and it would be just as well to remain cautious until it is. I can't see any obvious methodological change that would be generating an illusory swing, so it may just be that margin-of-error effects are exaggerating the trend slightly.
But that's not much comfort for Labour - to state the obvious, they desperately need to be gaining ground, and the mounting evidence that the swing is in completely the opposite direction will be greeted with unmitigated horror in McTernan HQ (which in normal circumstances is renowned for being such a happy, jolly sort of place).