OF the many factors that can cause a sudden change in public opinion, two of the most obvious are a sense of shock and a sense of momentum.

The shock when Britain unexpectedly voted to leave the European Union in 2016 pushed the pro-independence side in Scotland into a clear polling lead (albeit briefly), and there are many examples down the years of political parties enjoying a honeymoon after a thumping election win.

Both of those factors are firmly in play in our politics at present, because the SNP are basking in the afterglow of an election landslide, and Remain voters are reeling from the final realisation that Brexit cannot be stopped or reversed without independence.

READ MORE: Yes takes the lead in latest indyref YouGov poll

For those reasons it always seemed intuitively likely that the first full-scale Scottish poll since the General Election would show some sort of boost for the independence cause, and that it would be driven by Remainers switching to Yes in bigger numbers than before. But polling has an uncanny habit of blowing a hole in what seems intuitively likely, so the news from YouGov that there is now a Yes majority will be greeted with a degree of relief as well as jubilation.

The National:

A few may be slightly disappointed that the lead is only wafer-thin, but it must be remembered that YouGov have in recent years been one of two polling companies that have tended to produce better figures for No than other firms. Throughout 2017 and 2018, every poll conducted by YouGov had Yes somewhere between 43% and 45%, and yet during those years Survation and Ipsos MORI recorded Yes votes of as high as 47% and 51% respectively.

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It remains to be seen whether the methodological changes made by YouGov since the election have brought them into line with other pollsters, or whether the established differential will remain in place. If the latter, we can expect the Yes-friendly firms to show more substantial Yes leads.

Another big unanswered question is the extent of the Yes advance implied by YouGov themselves. On paper there has been a mammoth 7% increase in the Yes vote, but that’s measured from a YouGov poll conducted during the election campaign that was greeted at the time with considerable scepticism, because it showed a big slump for Yes that wasn’t replicated by other firms. It may be that was a rogue poll, in which case the 49% Yes vote reported by two YouGov polls earlier in 2019 should be regarded as a more meaningful baseline to judge the new numbers by.

READ MORE: Scotland to back post-Brexit independence, new poll reveals

It obviously matters a great deal whether the swing to Yes since the election is closer to 7% or 2%, and we’ll hopefully be closer to solving that mystery in the very near future due to a poll from another firm commissioned by my blog Scot Goes Pop, with the help of contributions to a crowdfunder from readers of The National.

The crumb of comfort that Unionists will be clinging to is YouGov’s suggestion that most Scots are opposed to holding an independence referendum either this year or next. However, the format of the question asked was arguably something of a cop-out, because it allowed respondents to express support for the principle of a relatively early referendum, while still feeling “reasonable” and “moderate” by not demanding one too soon.

The bottom line is that, with Don’t Knows excluded, a clear majority of respondents want a referendum within the next five years, which by any reckoning is well before the passing of “a generation” or “a lifetime” as insisted upon by Alister Jack, and will be comfortably within the SNP’s term of office if they are re-elected next year with yet another manifesto commitment to hold a referendum.