IT’S risky to makes assumptions in politics. There’s a fine line between sounding confident and crowing like a boxer before a world title bout. We all know what can happen next.

Surprisingly for a party that has generally played its hand carefully, there was a hint of bombast in the SNP’s response to the latest independence poll this week. Referring to an Ipsos Mori survey which showed 58 per cent of people favour independence – admittedly the highest pro-independence tally ever – the party’s deputy leader Keith Brown declared that this was a “landmark” moment which showed that independence had become “the settled will of the majority of people in Scotland”.

This is a brave choice of words, borrowing of course from John Smith’s phrase of 1994 to describe support for the establishment of a Scottish parliament, and is presumably designed to create momentum around the idea that independence, like devolution, cannot be stopped.

The trouble with the comparison is that prior to 1997, there were polls showing majority support for devolution going back years (as far back as the 1970s), not a matter of mere months, often at well above 60 per cent. There has been a shift in favour of independence this year, for sure, but just as unforeseen events have propelled the polls upwards, so they could also make them falter and dip again.

We are a long way off that referendum and in the midst of the most tumultuous period economically and socially since the war. That could turbo-charge support for independence or it could make it hard for the SNP to convince voters that independence won’t make tough economic conditions even tougher. And it’s far too early to say which way it will go.

For the pro-UK side, what makes the current surge for independence particularly troubling is that it can’t easily be attributed to just one thing.

Nicola Sturgeon has an approval rating to make God envious, which is obviously key. Voters have been impressed by her handling of Covid-19. This is in spite of death rates being high during Covid – Scotland, along with England and Wales, had excess death rates during the pandemic’s first wave that are among the highest of 21 industrialised countries, according to an Imperial College London study out this week. But voters seem to feel that she is doing her best and a lot better than Boris Johnson.

Women are now as likely to back independence as men, in contrast with 2014, which is probably down to Ms Sturgeon. Demographic change is also at work, as Prof Sir John Curtice points out, with people aged 16-24 much more likely than those aged 65-plus to back Yes.

But it’s not just about crisis leadership and the march of time, neither of which have much to do with arguments for long-term constitutional change. The Ipsos-Mori poll looks separately at which arguments in favour of independence people are most likely to agree with. The top two, backed by nearly two-thirds of those surveyed, were that people in Scotland want to take the country in a very different political direction to England and that Westminster cannot be trusted to work in Scotland’s interests. We can see the shadow of Brexit in this.

And I wonder if perhaps there is another factor at work. As well as seeing the Scottish First Minister leading the public health response to coronavirus here in Scotland, voters have seen Mr Johnson and his ministers – the UK Government in other words – doing the parallel job for England. This plays into a notion heavily promoted by the SNP, that Westminster is not really concerned about Scotland, but driven instead by English priorities.

Altogether it suggests the pro-independence messages are cutting through. If SNP strategists have been adding drams to their morning coffee these past two days, you can understand why. But “settled will”? Hardly.

This is just one poll. Other, simultaneous polls show overall support for independence at a lower level (ComRes says 53 per cent). That’s not a comfortable margin.

Those people who have switched sides in this debate to support independence are mostly not the sort to wear Saltire underpants. They may have warmed to the idea of independence, but do not necessarily feel an ounce of loyalty to the cause. How they will react to the coming economic upheaval is anyone’s guess.

How they will react to the coming economic upheaval is anyone’s guess.

The likely weak point for the SNP is the economy. Prof Curtice points out that only 15 per cent of former No voters are convinced that Scotland’s economy would be stronger outside the UK while three in 10 Yes supporters see independence as a major risk to the economy.

The former Yes campaign director Blair Jenkins has a point when he says the UK has stopped representing stability in the eyes of voters here in Scotland, with Brexit set to add another economic shock to the fall-out from Covid-19. Independence, by offering a way back into Europe, also seems like a safer option to many than taking a chance on buccaneering Britain. So, yes, the independence campaign could win the day.

But there is another equally plausible scenario: that after years of economic pain, voters might resist more upheaval.

The SNP’s economic plan will be critical. Government debt is now mountainous as a result of the pandemic and tax rises are coming. It’s in this climate that the SNP will have to publish a new economic blueprint for independence, having set the tone last time with a high-spending offer. This time, without reliance on oil revenues and with a new commitment to establish a stand-alone currency, it’ll be a tall order to be credible while offering eye-catching spending commitments and the promise of a generous welfare state.

But there’s something else as well, a curious finding by Ipsos Mori that perhaps points to another important pull factor for the UK. Sixty per cent said they were convinced by the argument that the countries of the UK had more in common than divided them, the single most supported argument for staying in the UK. Perhaps that is the flip side of the shared experience of coronavirus.

We need a clear blueprint for independence and a debate about it. The latest poll shows voters are engaged with that debate, but it doesn’t tell us which way they will ultimately jump.

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Read more: Poll puts support for independence at record high of 58 per cent