If constitutional politics was chess, Nicola Sturgeon would be contemplating the endgame. One by one, her opponents’ pieces have been captured. Move by move, she seems to edge closer to checkmate, or even to the moment when the United Kingdom’s grandmasters resign in despair.

Will there be another referendum on independence? Few doubt it. Will Yes prevail? Increasingly, smart money is moving in Ms Sturgeon’s direction. Her problem is that the argument over Scotland’s future is no mere intricate game with endless permutations. It is a lot more complicated.

Take the First Minister’s gambit, offered in a speech to the Scottish Parliamentary Journalists’ Association, to prise open the defences of Labour and the Liberal Democrats. Why, she asks, would Kezia Dugdale and Willie Rennie say that individuals in their parties can back independence in a referendum campaign when the two leaders rule out another referendum “forever and a day”?

It is a sensible question; that might be its defect. Ms Sturgeon is simultaneously offering to abjure a referendum “if there is no material change in circumstances”. She asks for a quid pro quo, one recognition of reality in exchange for another. It is more likely she will meet endless arguments over the definition of material change. Those arguments will not necessarily be illegitimate.

Similarly, the First Minister’s thoughts on the failures of the Yes campaign, while revealing, do not end the impasse between Unionists and Nationalists. She concedes what most accept: the shared currency scheme was unconvincing. Her predecessor, Alex Salmond, was notably less frank. But Ms Sturgeon gets to the heart of the problem: none of the alternatives would have fared any better.

She could have added a further truth: Unionist politicians will not treat the currency as a pawn to be sacrificed. It has a symbolic and emotional worth for voters greater than any mere piece on a board. A Scottish pound cannot, in any sense, compete. Like independence, it requires an act of imagination and faith. There is not yet a majority for those.

If this was mere chess, nevertheless, Ms Sturgeon would be praised for her patience and her ability to see several moves ahead. Her challenge to Ms Dugdale and Mr Rennie is based on a shrewd appreciation of the realities confronting two battered and bruised parties. Labour and the Liberal Democrats have been damaged hugely by blanket opposition to the Yes movement. The First Minister senses an opportunity.

The challenge for those with faith in a reformed Union remains. Ms Sturgeon believes her opponents know “what way the wind is blowing”. She thinks they sense their own weakness. It amounts to the oldest challenge in politics: put up or shut up. Labour and the Liberal Democrats will not be provoked, but sooner or later there will have to be a response. The “positive case” invoked so often during the referendum campaign will have to be stated.

Ms Sturgeon has given one hostage to fortune: the SNP still has no answer, it seems, to the currency question. Unionism needs more than that, however. It requires its own version of what the First Minister calls “a process of deep consideration” among Scots, one that causes them to value what they have rather than fear for what might be lost through independence.

Ms Sturgeon has made her move. There is everything still to play for. But there is no point in anyone pretending the game is not being played.