Although the new TNS poll shows a somewhat lower SNP lead in Westminster voting intentions than other firms have been reporting of late (albeit still enough to win the party two-thirds of the seats), the Scottish Parliament voting intention figures for the 2016 election have a much more familiar look to them. Admittedly, even on those, Labour have a higher reported vote share on the constituency ballot than other firms have been suggesting, but that wouldn't be enough to stop the SNP defying the PR voting system by powering to a second successive overall majority.
Constituency ballot :
Liberal Democrats 4%
Regional list ballot :
Liberal Democrats 6%
Now that the datasets have been published, we also have partial answers to the questions I posed last night - did TNS foolishly use 2010 recalled vote weighting (which we know is far less reliable than 2011 weighting), and is that the explanation for their Westminster figures being out of step with other pollsters? Horror of horrors, they DID use 2010 weighting, although they used 2011 weighting as well, which at least would have diluted the distortion caused. Nevertheless, it seems likely that this is at least part of the explanation for TNS showing a lower SNP lead than other firms - it probably can't explain all of the huge disparity with the 28-point lead suggested by Ipsos-Mori, but it might well explain all of the more modest disparity with other firms. The reason I'm having to use words like 'probably' and 'might well' is that there doesn't seem to be enough information in the datasets to make the calculation. All we have is an explanatory note at the top which reveals that 2010 weighting was used.
And there is another puzzle. Unlike the eccentric Panelbase poll in early October, TNS have used exactly the same weightings for both their Westminster and Holyrood voting intention questions. So the foolishness of using 2010 weighting can't explain the failure of TNS to replicate the finding of other firms that the traditional big difference between voting patterns for the two parliaments has more or less vanished. The explanation must lie elsewhere - perhaps in the face-to-face data collection method, or perhaps in the way TNS pose the questions.
Curiously, the Herald chose to headline the predicted turnout figures from the poll, rather than the voting intention numbers. I don't think there's any great surprise that many referendum voters are planning to give the general election a miss - after all, recent local council by-elections haven't really shown any 'referendum effect' in their turnouts. However, opinion polls haven't tended to be great guides in respect of turnout, so it's still perfectly possible (likely even) that Scotland will have a markedly higher turnout than the rest of the UK in May.