YES, I know it’s only one poll, and I know opinion polls vary, and I know the one at the weekend by YouGov showing a fall in support for independence could be an aberration and a blip. But that’s the point isn’t it? Between the hard cliffs of Yes and No, there’s choppy water, an uncertain place where one critical group of voters is prone to changing their minds. You could call them the nouveau nationalists.

But before we get into the details of who they are, and what they might do in the election and a second independence referendum, we should look at the details of the YouGov poll. What it said was 56% want to stay in the UK and 44% don’t, which is pretty much the same as the result in 2014. There have been changes since then obviously – and the YouGov poll is one of the biggest– but support for independence hasn’t collapsed. Far from it. The main lesson of the polls is that most of the support for Yes, and No, is ingrained at around the mid to high 40s.

Which leaves the bit in the middle: the voters who appear to have been shifting to Yes but may now be shifting to No before changing back to Yes again, who knows. There’s no exact political science here, but I think the results in 2014, as well as some of the voters I’ve spoken to, and the YouGov poll, provide some clues. On the whole, these voters in the middle are progressive, Left-leaning and inclined towards Labour (or at least used to be); some went over to Yes in 2014 and never went back; others, the nouveau nationalists, are more volatile. It’s this group that will probably decide how it all pans out in the end.

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As for trying to establish exactly who the nouveau nationalists are, the result of the independence referendum is important. At either end of the scale in 2014, you had those who vote Conservative and those who vote SNP; 95% of the Conservatives voted No and 86% of the SNP supporters voted Yes. But look at the figures for Labour – they were much more evenly divided at 63% for No and 37% for Yes; Labour voters, or at least voters on the left, are much more likely to be switherers, or sympathetic to Yes, or undecided.

I’ve seen this for myself when I’ve spoken to people campaigning on the ground for Yes. I particularly remember one woman I met: a lady from Ayrshire in her 50s called Marie, who switched to Yes and the SNP after a lifetime of voting Labour. Marie had always taken the view that socialism was an international movement and you should care just as much about the poor in Gateshead as you do for the poor in Glasgow and therefore vote No to independence.

But then she remembered two things. She remembered Margaret Thatcher condemning Nelson Mandela as a terrorist while Glasgow was giving him the freedom of the city. And she remembered the Scottish Government freeing the Lockerbie bomber Abdelbaset al-Megrahi. Both of those things, Marie told me, made her think: ‘Scotland can be different’.

Marie is self-evidently not alone: I’ve spoken to lots of Left or Left-adjacent voters who’ve come to the same conclusion. But for every Marie I’ve spoken to, I’ve also spoken to other voters on the Left who are not so certain or have come to a different view. Traditional Labour voters have gone both ways and those who’ve gone for Yes make up the vast majority of the new recruits to independence. Certainly, whenever I’ve spoken to people among the Yes grassroots, it’s hard to find anyone who’s ever regularly voted LibDem or Tory.

This is significant because it helps explain the vote in the middle-ground between Yes and No and its changeability, particularly in an election dominated by Brexit. Those on the Left are more likely to be Remainers and to be concerned about the effects of Brexit on society and there’s a crossover with Yes supporters– the YouGov poll found support for independence among those who voted Remain was 54%, more than twice what it was among Leavers.

The problem here for the Yes campaign is that left-leaning Remainers do not always reach the same conclusion about Scottish nationalism, Brexit and Labour, which may help explain the drop in support for independence. Nouveau nationalists who’ve been flirting with Yes are now faced with the chance of a Corbyn government (or at least a minority one in some kind of coalition); they are also faced with the possibility of a Tory win and a Boris Brexit.

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So what will they do? On the face of it, it would seem logical that the chances of Brexit and a Tory win would send progressive, Remainer voters rushing into the arms of the SNP and Yes, but it’s not as simple as that. As professor of politics Rob Johns pointed out to The Herald on Sunday, the Brexit effect may have highlighted the difficulties independence could bring. And for some nouveau nationalists, this is particularly troubling: if Brexit is bad for the economy and hurts the weakest in society, what on Earth will independence do?

Other factors may be at play in the dip in support for independence. Some voters may be leaning a little more towards Corbyn and therefore a little further away from independence because of the election campaign. But if that’s true, it won’t necessarily translate into votes for Labour in Scotland. That’s the weird, unpredictable thing about modern politics: Scotland used to be divided by Right and Left, now it’s divided by No and Yes and that’s had a profound effect on party loyalties; it’s all a lot more fluid than it was.

Which means, ultimately, that what the nouveau nationalists decide to do could be crucial. We already know that some voters in Scotland will vote tactically against the SNP, which is why support for the Tories in Scotland has been rising. But we also know that there are voters who separate a vote in a general election from a vote in an independence referendum, which is why some unionists will vote for the SNP this time because of Brexit.

But the real battle – in the general election and in another referendum on independence – is in the middle-ground over left-leaning, Labour-inclined voters. Another poll at the weekend showed that only 10% of SNP-minded voters and 12% of Tories might change their mind about who to vote for at this election, but for people minded to support Labour that shoots up to 30%. These are the voters in the choppy waters between Labour and the SNP, Leave and Remain, and Yes and No. What they decide to do will decide our future.