Remember how I said last night that "unless any newspaper is crazy enough to publish a poll on Christmas Eve, that really should be that"? Well, it turns out that the Daily Mirror is crazy enough, and they've just published a GB-wide Survation poll. We've had an unexpected little flurry of three GB-wide polls over the last 48 hours, so for the sake of completeness I'm going to do another Poll of Polls update - I'm sure this will be the last one of 2014 (although I seem to have said that somewhere before). It's based on one full-scale Scottish poll from Survation, plus six Scottish subsamples from GB-wide polls - three from YouGov, two from Populus and one from Survation.
Scottish voting intentions for the May 2015 UK general election :
SNP 44.1% (-1.7)
Labour 26.5% (+1.2)
Conservatives 16.5% (n/c)
Liberal Democrats 5.8% (+0.5)
UKIP 4.0% (+0.3)
Greens 1.7% (-0.2)
(The Poll of Polls uses the Scottish subsamples from all GB-wide polls that have been conducted entirely within the last seven days and for which datasets have been provided, and also all full-scale Scottish polls that have been conducted at least partly within the last seven days. Full-scale polls are given ten times the weighting of subsamples.)
The final Scottish subsample before Christmas proved to be the oddest of the lot, with Survation putting Labour well ahead of the SNP (by 48.9% to 27.1%, to be exact). That's only the second non-Populus subsample since the independence referendum not to have the SNP in the lead. However, there are three very good reasons why that finding is probably not significant -
1) It's based on a particularly small sample of 69 people, prior to weighting. For comparison, a YouGov subsample will typically be based on interviews with more than 200 respondents.
2) It's not bang-up-to-date. It may be the last poll to be published before Christmas, but it wasn't the last one to be conducted. The more recent subsamples from Populus and YouGov have continued to show the more familiar pattern of a huge SNP lead.
3) Survation's fieldwork even partly overlapped with their own full-scale Scottish poll, which showed a mammoth 24% SNP lead.
There's also the fact that Survation weight their results by recalled Westminster vote, which we know harms the SNP. But that's something all firms other than Ipsos-Mori do in their GB-wide polls by one means or another (if they don't literally weight by recalled Westminster vote, they weight by Westminster-centric party identification figures).
The bottom line is that it's almost certainly just a freakish result, but it's one more drop of evidence to be put into the mix with all the other drops, and the overall picture we're left with is the SNP lead of 17.6% that you see in the Poll of Polls.
All the same, this is a timely reminder of how the huge divergence between Scottish and English voting intentions may be making GB polls less reliable. Labour have a 3-point lead across Britain in the Survation poll - but if we assume the Scottish subsample is just a freak caused by normal sampling variation, that lead may not be particularly meaningful.
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A small technical note : I realised tonight that I've been looking at the wrong table in previous GB-wide Survation datasets - I had assumed that Survation use the numbers which have been adjusted for the "spiral of silence" in their headline results, but it appears that they actually use the unadjusted numbers instead. That means there may have been slight inaccuracies in a small number of previous Poll of Polls updates. However, the inaccuracies will have been very slight indeed, so I'm not going to torment myself by trying to retrospectively correct them.
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I know we're all reeling with disbelief after the terrible events in Queen Street and George Square, but I'd still like to wish all readers of this blog a very Happy Christmas.