EVERYONE looked like they were in a pretty good mood as they headed into the SNP conference in Glasgow at the weekend - and why wouldn’t they be? The delegates had only just heard about some new opinion polls that seem to show that Brexit has boosted support for independence. Not only that, one of the polls suggests that, in the event of a no-deal Brexit, 52 per cent of Scots would back independence. What’s not to like?

But haven’t we been here before? In fact, I’m tempted to say we’re stuck in a bit of a time loop on this one, with the same events happening over and over again. Nicola Sturgeon said on Sunday that support for independence was at historically high levels, but in early September 2014 a YouGov poll showed support for yes at 51 per cent; this weekend’s survey for The Sunday Times on the other hand shows that, even with a no-deal Brexit, support for independence would be lower than that, at 48 per cent. “Historically pretty much the same” might be a better description.

However, it’s worth taking a look again at exactly what the new polls say. The first one, by Survation, found that, if there were an independence referendum tomorrow, 46 per cent would vote yes and 54 per cent no. But if the UK leaves the EU as planned next year, that changes to 50 for yes and 50 for no – and it changes again if there’s a no-deal, with 52 per cent backing yes and 48 per cent no. The other survey, by Panelbase, found a similar rise: if the UK left the EU without a deal, support for independence would increase from 45 per cent in 2014 to 48 per cent, while support for the Union would fall from 55 to 52.

On the face of it, these look like encouraging figures for the SNP, with Brexit pushing support for independence in the right direction. But if I were a Scottish Government strategist, I might privately be a bit worried. In fact, I might even have suggested to my bosses that they keep quiet about the Survation poll, which was commissioned by the SNP, for the simple reason that it doesn’t show enough of what they need it to show.

The problem is that the surveys do indeed appear to indicate support for the SNP and independence going up. But they also demonstrate something more disturbing for the party, which is that the expected Brexit effect on support for independence simply isn’t happening, or at least it isn’t happening to the extent that Nicola Sturgeon needs it to.

This lack of a significant Brexit bounce also emphasises the dilemmas faced by Ms Sturgeon. The party members who traipsed into the conference on Sunday and marched through Edinburgh on Saturday are nationalists because their heart tells them to be, but the First Minister takes a much more mathematical approach to the situation, led by the numbers and the probabilities.

This is why we saw her shifting her position on a second EU referendum at the weekend. The difficulty for Ms Sturgeon is that she’s a declared supporter of the EU, but the very thing she appears to be fighting – Brexit – may also offer her the best chance of getting what she really wants: Scottish independence. This means she has to be careful not to fight Brexit too hard, and yet she can see that a consensus is building for a second EU referendum that it would look odd for the SNP to oppose. And so Sturgeon the mathematician nudges forward and says her MPs would support it in the Commons. Their leader there, Ian Blackford, gave the game away when he addressed the subject. “We will not obstruct a second vote on Brexit,” he said – hardly the words of a passionate anti-Brexiteer.

The weekend’s opinion polls throw up similar strategical problems on when to hold a second independence referendum. They do appear to show a small Brexit effect and, anecdotally, I’ve noticed it among friends and family. Quite a few who voted no in 2014 have told me, over a coffee (but usually a beer), that Brexit means they might vote differently next time. But a hypothetical vote in the pub, or indeed in an opinion poll, is not the same as the real thing, when all the old economic realities would come back. Indeed, they might be even more intense in a post-Brexit world with switherers asking themselves whether, having come out of one economic union (the EU), they want to risk coming out of another (the UK).

The fact that the small rise in support for independence is based on these hypotheticals leaves Nicola Sturgeon with three equally risky options. The first is to call a referendum before the next Scottish elections in 2021 but that would be rejected by Theresa May and probably even Jeremy Corbyn if he were PM given the pressure he would face from his Scottish wing. The SNP might be able to gain some traction by fostering a grievance about the referendum being rejected in this way, but option one is essentially a dead end.

The second option is one that no one expects to happen – a Catalan-style, unofficial referendum – but it’s the third – delay the referendum until after 2021 - that is the most likely. The theory behind it, as far as some SNP strategists are concerned, is that this allows more time for Brexit to convert more no voters. The aim would also be to win the 2021 election based on a promise to hold another independence referendum, which would make it impossible for a Prime Minister to say no.

This is Nicola Sturgeon’s preferred option – she just hasn’t said it yet. Indeed, it’s never going to be easy for her to say it as long as thousands of nationalists are marching through Scottish cities. She also knows that delaying is risky – the Panelbase poll predicts that the independence-supporting parties will lose their majority in 2021; there is also a danger that voters will simply get used to being outside the EU; Brexit will become the new status quo.

And then there’s the awkward reality that, whatever your analysis of the new polls, there is still a working majority in Scotland opposed to independence. Ms Sturgeon’s gamble – as yet undeclared – is that this will change by 2021. The problem is that, even in the face of a Tory-imposed Brexit, both sides in Scotland (nationalist and unionist) look pretty resistant to change.