I was talking to a No voter recently and she said this: “When I look at how Boris Johnson is handling coronavirus, and then look at how Nicola Sturgeon is handling it, I think maybe independence would be for the best.”

You hear it more and more, this expression of newfound openness to Scotland going it alone. It’s not a full-throated cry of devotion; it’s not even unqualified support; but it could be the beginning of something highly significant.

It’s perhaps worth mentioning that my friend and her husband are both English, with no family ties to Scotland, though they have lived here for several years. Research on the linkages between national identity and support for independence shows that those who were born elsewhere in the UK are less likely to support independence than those born in Scotland.

But now a second trend is emerging that is cutting across those ties of national identity. It feels as if independence is becoming more firmly associated with another form of identity, one based on progressive values and competent government, and a lot of people – like my friend – seem to see Nicola Sturgeon as embodying it.

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YouGov’s eye-popping new poll, that puts support for independence on 53 per cent and support for the SNP on 57% in the constituency vote, is perhaps most notable for what it reveals about attitudes to Ms Sturgeon. Her approval ratings stand at +50 compared to -50 for Boris Johnson (this, incredibly, in spite of the Scottish exams fiasco that was unfolding as the polling was done). It echoes the findings of a Panelbase poll, in which Scottish voters praised Ms Sturgeon for her handling of Covid while criticising Mr Johnson’s effort.

Now, on one level this is a curiosity. The virus tore through care homes in Scotland as it did in England. Scotland like England is one of the hardest hit countries in Europe when excess deaths are considered, according to the Office for National Statistics (though the increase in Scotland’s death rate compared to previous years is lower). Nicola Sturgeon has been more cautious about re-opening the economy and more successful at driving down the infection rate latterly, but with hindsight these are likely to be seen as shades of contrast rather than wholesale differences.

Yet Nicola Sturgeon has emerged as a sort of sainted figure while Boris Johnson seems to be widely derided in Scotland.

This partly predates the pandemic, of course, and has to do with Brexit, itself a proxy debate about values. Scots didn’t want Brexit but are getting it anyway, thanks largely to Mr Johnson. That explains the slow trickle of exasperated Remainers converting to the Yes cause prior to the spring.

But not even Brexit explains the latest surge of support for independence. The latest polling shows that both Leavers and Remainers who once voted No are now more likely to back Ms Sturgeon. What gives?

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Character. OK, wind back a moment: partly it’s simply because she’s the Scottish First Minister and the Scottish First Minister will always be seen as more committed to Scotland than the UK Prime Minister.

But character is critical. Character is big this year, you might say. Leaders are being judged all over the world on whether they have what it takes to manage an emergency. Nicola Sturgeon is perceived as a hard worker and a decent sort, even by people who don’t vote for the SNP. She has been seen standing at the podium delivering briefings day after day throughout the pandemic. Where Mr Johnson sets off Scots’ manure detectors, seeming at times ill-prepared and vague, Ms Sturgeon has been across the detail and shouldered responsibility for her government’s response.

She’s made mistakes (several) but Scottish voters seem to think: she’s doing her best, which is more than you can say for him.

In the background, meanwhile, there is a broader story about the divergent politics of the two.

We saw it this week over Mr Johnson’s response to migrants crossing the English Channel, with Mr Johnson using terms like “criminal” and “illegal”.

In doing so, he was nodding to the hard right members of his own parliamentary party, 25 of whom signed a letter characterising migrant men, women and children as “invading” Britain.

Nicola Sturgeon does not use language like that; indeed, at Holyrood generally, such language is rare.

The more Mr Johnson appeals to his base, the more out of step he seems with Scotland’s politics.

The result of all this? That Ms Sturgeon appears to be achieving the Yes campaign’s greatest goal: winning over soft No voters, the only credible long-term strategy for winning an independence referendum. Her apparent success boots into touch her critics on the whining wing of the Yes movement.

But there’s a problem: if the Yes cause is now an unlikely personality cult for the cautious but determined figure of Nicola Sturgeon, then what happens if her popularity wanes?

The rise in support for independence has shadowed Sturgeon’s own rising popularity. If seen as a personal vote for her, rather than for the principle and prospectus of independence, then suddenly that towering support for Yes starts to look rather more precarious. If we pass “peak Nic” and her ratings start to slide (the Salmond inquiry and the recession will make for a bumpy few months) then it follows that support for independence will come down too.

Perhaps, then, it would be wise of independence supporters to see the current polls, not as proof that they have won the argument, but as a sign that more people than ever before are at least prepared to listen.

Ms Sturgeon’s critics in the movement would like a more hardline approach to independence but her pragmatic and level-headed style is what appears to be winning over those critical middle ground voters.

Nicola Sturgeon can expect a relentless barrage of criticism from now till election day next May.

But she can count the UK Prime Minister as her finest campaigning asset. The contrast between them is helping boost her own popularity and with it the cause of independence.

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