Before today, there had been eleven polls since the Holyrood election showing a No lead (albeit for the most part a slim No lead), one showing a tie, and just one showing a slim Yes lead. The big majorities for independence that we got so used to in 2020 had begun to look, at least for the time being, like a thing of the past. And yet, all of a sudden, today brought word of a poll that wouldn't have looked at all out of place one year ago.
Should Scotland be an independent country? (Ipsos-Mori / STV, 22nd-29th November 2021)
Yes 55% (+5)
No 45% (-5)
Can one extremely good opinion poll negate the previous thirteen? (Or, to be more precise, eleven of the previous thirteen?) In usual circumstances, the answer would be no - the suspicion would be that this is probably an outlier result caused by random sampling variation. At the very least, we'd be cautiously waiting for one or two more polls before jumping to the conclusion that the new trend is real. But with Ipsos-Mori, in general the only firm to conduct Scottish polls by telephone, it's a different story. There's still no consensus on whether telephone polls are superior to online polls, or vice versa, and the only reason the vast majority of polls are conducted online is to sharply reduce costs. If the only telephone poll you have shows a picture that is wildly out of line with the sea of online polls, there are very good reasons for seriously considering the possibility that the telephone poll is actually the accurate one - or closest to being the accurate one.
To be clear, there's no great surprise in Ipsos-Mori showing a Yes lead - in recent years they've been on the Yes-friendly end of the spectrum, so a slim No lead with Panelbase or YouGov might be expected to translate into a slim Yes lead with Ipsos-Mori. But what is genuinely startling is that Ipsos-Mori are showing a completely different trend from the online firms. The No leads in the online polls have generally represented little or no change since the latter stages of the Holyrood campaign, whereas today's poll suggests there has been a massive Yes resurgence since the election. That seriously calls into question the story we have been telling ourselves, and more importantly the story the media have been telling us, about the state of public opinion over the last few months.
Having said all that, the slight health warning that needs to be added is that data collection by telephone is not the only thing that sets Ipsos-Mori apart from other polling companies - they also have a different attitude to weighting by recalled vote. So in theory that could be an alternative explanation for the disparity.
As Marcia has pointed out in the comments section below, there is a clear Yes majority in today's poll even if Don't Knows are left in: Yes 52%, No 43%, Don't Know 4%. It's to be hoped that the SNP leadership don't repeat the mistake of last year by treating this Yes lead as a precious piece of china that might break if anyone so much as sneezes, and instead use it to loudly demonstrate that there is a strong appetite for a choice on independence in the near future.