So, Scotland will quit the United Kingdom if the vote in June goes against remaining in the European Union, will it? If you are a fervent Scottish nationalist you may be hoping so. If you are a worried pro-EU unionist you may be fearing so. And even if you are neither of these, you may have got the general impression that it is likely. But I say this: don’t jump to conclusions.

Interviewed by Andrew Marr on Sunday, the SNP leader Nicola Sturgeon came close to promising a second independence vote if Britain votes to leave. The shift in Scottish opinion would be “inescapable” and there would “almost certainly” be a second vote, she said. The next day the party’s Westminster leader, Angus Robertson, said Scots “will demand” a referendum if they are “forced out” of the EU.

Now, it is true that all these statements leave some wiggle room. “Almost certainly” is not the same as “certainly”. And while some Scots “will demand” a second independence referendum, some will not. The SNP has certainly rattled its sword but it hasn’t absolutely raised its standard. Any decision about a second Scottish vote is still likely to await the counting of votes in June.Here’s where the problems start, however. For one thing, the difference between Scottish and UK or English opinion is often exaggerated and occasionally romanticised by some Scots. So it may be worth remembering that back in 1975, when the UK last voted on Europe, Scots were pro-EU by 58% to 42%; but the English actually voted pro-EU by a much larger margin of 69% to 31%, and the only two of the 68 UK counties that voted no were Shetland and the Western Isles. Back then, the SNP itself was also for out.

That’s all 40 years ago and much has changed radically, of course. Today Scotland is solidly in favour of remaining in the EU while UK-wide opinion is much more evenly divided. But the evidence for saying that a UK vote to leave the EU would boost support for independence is extremely fragile, as Professor John Curtice – most people’s go-to pollster on these questions – has written.

Moreover, though we don’t often hear about it, Euroscepticism is alive and well and living in Scotland on both the right and the left of the political spectrum, and not just because Ukip may be about to win its first seats in the Scottish parliament in May. This week Curtice classed 60% of Scots as Eurosceptic, in the sense of thinking the EU is too powerful, compared with 65% of UK voters – not a huge divide. So it doesn’t follow that a UK leave vote would send Scots rushing into a second referendum so that they could stay in an EU whose stretch they dislike.It is also worth remembering that the only thing on the SNP’s agenda at the moment is the Scottish parliament election on 5 May, not the referendum six weeks afterwards. The SNP needs to mobilise its members, some of whom are in politics largely for a second indyref, and it wants other Scottish voters to see the party as Scotland’s champions. So it suits the SNP to be making threats to London, just as it has been doing over the much more real issue of Scotland’s fiscal deal with Whitehall this week. Seen this way, a second independence vote that may seem inescapable before polling day may become a bit more escapable afterwards.

Sturgeon will only call a second referendum when she thinks she can win it, or when she is forced by party to do so

Yet even if all the cards fall exactly where advocates of a second Scottish referendum would like them to fall – the SNP re-elected in May, a narrow UK leave vote in June, a strong Scottish majority to remain, a cast-iron grievance about being forced out by England – there are still two huge reasons for the SNP to look before they leap.

The first is process. Sturgeon doesn’t have the power to call a referendum; the UK parliament does. Would it agree? If she tries to press ahead anyway in the name of injustice, the courts could stop her, and stop the use of public funds. Scotland’s civil service might be debarred from working on the referendum.

But suppose all this is magically dealt with. As in 2014, the voters would need to know what they were being offered in the independence vote. In 2014, that included retaining the pound and an oil price of $110 per barrel. But would either part of that be plausible the second time round, with oil at about $30 a barrel and sterling as the currency both of the rest of the UK leaving the EU and of Scotland trying to stay in?

If not, the SNP would have to offer independence based on either a separate Scottish currency or the euro. If the latter, then the SNP would be committing itself to the strict borrowing limits that go with eurozone membership. And that, as Alex Salmond’s former policy chief Alex Bell argued this week, could only be squared by an SNP commitment to higher taxes as the necessary price of Scottish EU membership, just when the UK was cutting taxes to create an advantage over the EU.

Supposing once again that all these difficulties were magically overcome and Scots nevertheless voted for independence, that’s still only the start. By the time the second vote took place, the UK would be negotiating its way out of the EU. But, as Bell points out, the sovereign state of Scotland could not exist until it had negotiated its way out of the UK. That may take up to two years. In the meantime, the negotiations might be tripartite – with the UK negotiating to leave the EU and Scotland negotiating to stay in. There would be nothing friendly about the process. And at the end of it, there would have to be a referendum in Scotland on the terms of staying in – and there could be a no vote.

Underlying all this is the second problem Sturgeon faces. She will only call a second referendum when she thinks she can win it, or when she is forced by party to do so. Right now, not enough Scots support independence – 45% in 2014 and 47% in the most recent poll. Failure to win a second referendum would close the independence issue for decades – just as did in Quebec – and could mark a point of decline for the SNP.

All this is precisely why Sturgeon has been careful not to make any outright commitment to a second poll in recent months. No wonder she said this week she will be campaigning in England for a UK vote to remain in Europe. A vote to leave would be a disaster for the SNP.