I've been reading through some of the comments on UK Polling Report about the new TNS poll, and Roger Mexico (who has occasionally posted here) is largely dismissing the concerns over the unusual weighting procedure that was used. He's a very intelligent guy, so it's not completely impossible that something is going over my head, but on the face of it his argument seems full of holes to me -
* He points out that the Ashcroft constituency polls used 2010 vote recall weighting only, which ought to be even worse than the combination of 2010 and 2011 vote recall that TNS used - and yet Ashcroft still painted a devastating picture for Labour. But so what? Without the dubious downweighting of the SNP vote, the Ashcroft polls would have been even worse for Labour (in all likelihood the SNP would have been ahead in Glasgow North-East along with the other fifteen seats surveyed), and who is to say that wouldn't have been a more accurate finding? Simply saying "crikey, these numbers look quite bad enough as they are" is scarcely a guarantee of accuracy.
* He claims that we "know" SNP supporters are more eager to respond to polls than others, which will lead to them being over-represented in Ipsos-Mori polls, due to Ipsos-Mori being the only firm that doesn't weight by vote recall at all. Therefore, at least some of TNS-BMRB's downweighting of the SNP based on vote recall is entirely justified. But do we really "know" that? Isn't the "eager nationalist" theory rather contradicted by Ipsos-Mori's status as one of the two most No-friendly pollsters throughout most of the long referendum campaign? If anything, it looks like the opposite phenomenon may have been occurring for a prolonged period.
* He suggests that TNS-BMRB's decision to ask for both 2010 and 2011 vote may make people's recollection of how they voted more accurate, thus removing the objection to 2010 weighting. That notion is extremely speculative, but even if it was true, it would only work if the 2011 recall question was asked first. If people's recollections of 2010 are faulty, the problem is hardly going to be rectified by a different question that is asked afterwards. As it turns out, the TNS datasets clearly show the 2011 question was not asked first.
* In dismissing the complaint that there is no way of telling from the TNS datasets what impact the 2010 weighting has had, he claims that "equivalent" information is given - and then points to numbers showing that the SNP and Labour were downweighted by roughly the same amount from their vote shares among the raw unweighted sample. Frankly, that's a complete red herring. Throughout the referendum, TNS were more often than not producing Labour-heavy raw samples. It's quite possible that normal demographic weightings (and indeed 2011 vote recall weighting) boosted the SNP in this poll, but that was completely offset by distorted 2010 vote recall weighting. There's no way of knowing that for sure, though, because as far as I can see the information simply isn't available in the datasets - neither in literal nor in "equivalent" form.