For almost twenty years, the Scottish Social Attitudes Survey has been asking an annual question on constitutional preferences for Scotland - a question that would, if asked by a regular pollster, be rightly blasted as being absurdly leading, and pejorative about independence. However, the advantage of rigidly sticking with such an ill-judged question is that we can be sure than any long-term change in public opinion is genuine, rather than an illusion caused by a tweaking of the words. The change we've seen in recent times is therefore not only quite staggering, it's also meaningful.
For the second year in a row, the new survey has produced a record high figure of support for independence. On both occasions, the previous record has not just been broken - it's been completely obliterated. The latest figure of 46% is an incredible 11% higher than any survey up to and including 2015 had recorded.
Independence 46% (+7)
Devolution 42% (-7)
Direct rule from London 8% (+2)
One of the great mysteries of the 2014 referendum campaign was the cause of the Great Polling Convergence right at the end. Were online firms like Panelbase correct that there had been only fairly modest movement towards Yes over the course of the long campaign? Or were the face-to-face polling firms like Ipsos-Mori and TNS (plus YouGov, the odd one out of the online world) correct in reporting that there had been a massive swing? Or was the truth somewhere in between the two extremes?
The Social Attitudes Survey is conducted in a different way from regular polls, and the pejorative language used in the question about independence also makes it very hard for respondents to express support unless they are truly committed. The results tonight therefore lend some credence to the notion that the mind-boggling and lasting swing towards Yes we've seen in face-to-face polls over the last three years (and confirmed again by last week's Ipsos-Mori poll) has been caused by genuine movement in public opinion on the ground, and that online polls may not have fully picked up on the sea-change that has occurred.
Elsewhere in the survey, there's evidence of surprising levels of Euroscepticism among Remain voters from last year, which leads Professor Curtice to conclude that pro-EU sentiment may be too weak to make No voters from 2014 switch to Yes. However, it should be noted that one-third of respondents who are currently both pro-EU and anti-independence did not say that they feel the EU should have fewer powers. If the Yes campaign can make serious inroads among those people, it may be enough to build up a decisive lead.
More realistically, Yes are probably going to need the support of a significant minority of Leave voters, which will cause some strategic difficulties in terms of messaging. But I struggle with Professor Curtice's argument that this means the SNP have misjudged the timing of a second referendum and should instead have waited for demographic shifts to work in their favour. Curtice of all people should know that Yes cannot just 'bank' the support it already has, and complacently wait for older No voters to die. The bullish fifty-something Yes voter of today may be a No-voting sixty-something of tomorrow, newly fearful about his or her pension. Current Yes supporters of all ages may think twice about embracing another major constitutional upheaval after several years of turmoil caused by a Hard Brexit. And in any case, the "right time" to hold a referendum can only ever fall during a period when there is a pro-referendum majority at Holyrood. We're living through one of those periods at the moment, but there's far from being any guarantee that we will be a decade from now.