TNS Scottish poll

This morning TNS released a new Scottish poll. Topline Westminster voting intention figures are CON 16%, LAB 31%, LDEM 4%, SNP 41%, GRN 6%, UKIP 2% (tabs here). Under normal circumstances these would obviously be good figures for the SNP, but these are not normal circumstances and it's a much smaller SNP lead than that suggested in recent polls by YouGov, Survation and Ipsos MORI.

Unlike their GB polls which are now done online, TNS's Scottish polls are still done using face-to-face interviews. This means the fieldwork tends to take significantly longer, and the polls are then often not reported until a week or so later. The fieldwork for this poll was conducted between the 14th January and the 2nd February. This means the Survation and MORI polls from last month which showed 20 point and 28 point SNP leads for the SNP had fieldwork done at the same time as the start of this poll. The YouGov poll last week which had a 21 point SNP lead had fieldwork done at the same time the fieldwork for this poll was finishing (so is mostly significantly newer than this one!). What this means is that much of the reporting and headlines on this poll are just rubbish - the poll does NOT show the SNP lead falling. It shows a smaller SNP lead - this may well be for methodological reasons, or perhaps a bit of random sample variation, but given the respective timing of the fieldwork it cannot be that public opinion has changed since the previous poll showing a 21 point lead, as this poll was mostly conducted before that one. It's a thoroughly bad idea to try and draw trends between polls conducted using very different methods anyway, but certainly check when the fieldwork was done and get them in the right chronological order.