Here are four truths about Scottish politics. The nationalist SNP commands the stage, reinforced by its latest Holyrood election mandate in May. Its leader, Nicola Sturgeon, is Scotland’s most admired political figure by far. Boris Johnson is a big turnoff for Scots. And more Scots want a second independence referendum by 2026 than do not. Sound familiar? They should. All four things have been true in some form or other for a long time now. The SNP has been dominant for 14 years now. Sturgeon has reigned supreme for seven. No Conservative prime minister has been popular with Scots. Demands for a second referendum have revved up since the 2014 No vote, especially after Brexit. So does that mean there will in fact be another independence vote soon? Many say yes. They depict the demand as politically unstoppable. Yet it all depends on which side holds the stronger card. Some polls give the nationalists a boost – yesterday’s Ipsos Mori poll has 55% support for independence. Most others counsel caution: a week ago YouGov had independence trailing on 47%. Scots tell the pollsters they want support to be consistently at 60% before Sturgeon calls a second vote. She remains well short of achieving that. While individual polls remain volatile, the overall picture has paradoxically become more settled. The immediate independence drive appears stalled. The return of Covid-19 boosts Sturgeon as a leader but that boost pushes independence down the agenda again. All this could continue for at least another year. That doesn’t mean there will never be a second referendum, let alone that there ought not to be one. But it does mean, as Galileo might have said to the Inquisition, that it still isn’t moving. To write this will provoke the usual abuse from supporters of independence. Looked at dispassionately, however, it is the case, and one good poll for the independence cause does not change it. More significantly, leaders on both sides in the argument know this too. Their actions can only be properly understood in that light. This is a time for political calculation. It may be less exciting than some want, but it is in some ways more fascinating. The underlying reality is that Scottish opinion still divides down the middle about independence. Smart strategists have long recognised that the resultant standoff requires delicate judgments. Nationalists don’t like the standoff, of course, while unionists do. Each must nevertheless be highly aware of the danger of overplaying their hands. Canny nationalists know they risk alienating middle-ground opinion by obsessing about independence over everything else, especially during Covid. Unionists know that Johnson charging around Scotland trying to stick a union flag on everything is a guaranteed vote-loser. If they didn’t know it before, they certainly do after Johnson’s 80% dissatisfaction rating in the Ipsos Mori poll yesterday, a record low. Gordon Brown argued earlier this year that Scottish opinion divides not into two but three. On many issues, diehard nationalists and unionists frame a group in the middle that is larger than either of them. These middle-ground voters, people whose politics are not wholly defined by the constitutional question but by other values too (many of them shared with people across Britain), will shape any outcome. They remain very much up for grabs. In 2014 they tipped the balance against independence. The nationalists have to change that – but they have not yet succeeded. Until they do, a second referendum remains an uncertain enterprise in which a second defeat would shake Scottish politics to its foundations. Never underestimate the ability of the SNP and the wider independence movement to shift opinion during a campaign, especially while Sturgeon remains at its head. Even so, more thoughtful nationalists acknowledge the difficult reality – and have done so even in the week of the SNP’s recent virtual party conference, in which all its leaders have been compelled to talk up the referendum as urgent business. In reality, there is more light and shade in all this than many would like. Inevitably, Sturgeon’s judgment, and that of the small circle around her, is crucial. Not many nationalists would go as far as one seasoned Scottish political observer did the other day, claiming to me that “Nicola’s commitment is Augustinian; give me a referendum, but not now.” But it is undeniable that Sturgeon – caught between the fervour of her followers and the caution of the voters whose support she needs – is being forced to play the long game on the second referendum. True, there have been moments when events were moving the nationalists’ way – especially in the early aftermath of the Brexit vote. But this has ebbed now, and Brexit, with all its uncertainties, is no longer the nationalist recruiting sergeant that it was. Nor has Sturgeon’s handling of Covid translated into an enduring boost of support for independence. At the height of the pandemic, especially when compared with Johnson, Sturgeon soared in the polls. In August 2020 her approval ratings reached +50. Today they are down, at +12. That’s still far better than anyone else, but it is a reminder that when Sturgeon is judged on other things, including the SNP government’s often poor domestic record, the aura can sharply diminish. The result, perhaps surprisingly, is that UK ministers currently think they have acquired more of a handle on the Scottish question than one might assume in the light of Johnson’s unpopularity and the SNP’s ascendancy. They have done it by a policy of what Victorian imperialists might have called masterly inactivity. Taking care not to inflame the situation needlessly, and trying to avoid outrageous ineptitude may not set the bar high for the UK government, but recent months have been marked by what ministers are more likely to call strategic patience. As long as there is no fervour for independence outside the core vote, UK ministers believe they can play it long. In practice, that means Scotland faces a constitutional poker game, not a battle for freedom. Both sides have to think several moves ahead. The central fact is that there will be no UK government agreement to any request from Sturgeon for a second referendum this side of the next UK general election. That election may not be until spring 2024. What will follow is a tough two years of mounting pressure on Sturgeon from SNP activists to go it alone in a referendum that opponents will dismiss as unlawful and which voters may regard as a misjudged priority. Much rests on the decision she must take. In the fight for the future of the United Kingdom, it is less a question of which side has right on its side, and increasingly a question of which side will blink first. Martin Kettle is a Guardian columnist