Anyone tempted to regard Nicola Sturgeon as Alex Salmond by other means is, I think, making a very big mistake.

Those observers misunderstand the individuals, their ambitions, and what has been going on in Scotland just lately.

Yesterday, the country's recently-dominant politician took his leave of the party leadership with a fair summation of how things stand. Judging by Mr Salmond's speech in Perth, the SNP regards a referendum defeat as no worse than the second-biggest opportunity it might have hoped for. It treats all talk of home rule as a binding commitment to be enforced in - for why not? - the national interest.

The SNP means to be the largest Scottish party in any legislature available. It intends to treat any quibbling within the Smith Commission, or any European shenanigans at Westminster, as the justification for another vote on Scotland and the UK. Oddly enough, nevertheless, these are not the important details. There's this: the SNP has thought this thing through.

One clue would be the speed with which Mr Salmond resigned after the independence referendum. He acted like a man who had already contemplated the consequences of a No vote. He was not giving way to a rival by handing in his notice, but passing responsibility to a political partner who might - for let's be blunt about it - succeed where he had failed.

On paper, this dreich November, you could wonder about that. The SNP's opinion poll ratings, like its ever-increasing membership, qualify as phenomenal. The cliché is already in place: who really lost the referendum? The Nationalists, with their 85,101 members, behave like a party working out the next moves. Labour scrambles to salvage what it can from the wreckage.

It's not the obvious moment for Mr Salmond to stand aside. Unlike most defeated campaigners, he has yet to question his own choices. He has not pawed through the entrails of the Yes movement, confessed to a single misjudgment, or even hinted he might have done this or that better. He did not win independence, but he scattered its enemies. That, for now, will do. The next phase belongs to Ms Sturgeon.

Those Unionists who grumble about a "neverendum" miss this point by a country mile. Did someone introduce a rule to say you only get one chance at national self-determination? Do parties pack up after a single lost vote? The Yes voters who believed things ended "for a generation" on September 18 were few. Yesterday, in various interviews, Ms Sturgeon made that much clear. For her party these remain questions of when and how, not if or why.

But Mr Salmond lost. "How" will have to be fashioned differently henceforth. For the SNP, there will have to be - there already is - an analysis that gives all credit to the soon-to-be-former First Minister, but need not spare the programme he fashioned. Currency, corporation tax, terrorised pensioners and, crudely, "women": sooner or later, while Westminster politics unravels, Ms Sturgeon will have to address these issues.

Some things are already clear. The attempt to unite the broader Yes movement with the SNP in a "Yes Alliance" born of candidacy arrangements and amended membership rules involves lots of tricky hurdles. There's no reason why it wouldn't work. There are lots of predictable reasons why it could fall apart. What matters, for now, is that Ms Sturgeon is prepared to subordinate her party to a cause. Mr Salmond seems to agree.

Secondly, the SNP under its new convener will not maintain the Conservative Party in power in Britain. Even within the Westminster bubble, that will become big news in the months ahead. It involves no real change in Nationalist policy, but it sees Ms Sturgeon hammer her colours to the mast.

How do you keep Britain together if one part of the polity is entranced by a Tory/Ukip squabble when king-making depends on a difficult province whose voters despise those factions? The voters of England who not so long ago were exasperated by noisy Jocks might have to think again. One of those strange, distant minor parties could yet have a major voice.

No matter: Ms Sturgeon has made her case. If the SNP pick up lots of seats next May, and if the Commons reflects a hung Parliament, David Cameron can go whistle for Nationalist support. That's important. Once the quibbling over the difference between red Tories and blue Tories subsides Ms Sturgeon will still be saying something profound about the UK and its vaunted partnerships. Something like: "Ignore us if you dare".

If she will not tolerate Tories, what about Labour? Amid all the media-conjured noise over Jim Murphy's attempts to seize the Scottish branch office, that counts as the most important decision, thus far, by the First Minister in waiting. The SNP's Westminster group might support Labour, she speculates, "issue by issue". Some version of confidence-and-supply is implied, a deal that places all the onus on the beggar, not the chooser.

Does Scottish Labour have a view on that possibility? Amid the travails of Ed Miliband, would it stoop to an arrangement with the despised separatists? And if it would - for of course it would - what price would it swallow for the sake of a wee go at running Westminster? London could live with it, no doubt, but how about Mr Murphy? What would then be the point of voting Labour in Scotland?

Too many observers forget too easily that Ms Sturgeon negotiated the Edinburgh Agreement on behalf of the SNP. She is also a veteran, at just 44, of the kind of work that needs to be done to keep a minority government on the road. In glib shorthand, she is "more left-wing" than Mr Salmond. That's broadly true, but it's a small part of the bigger truth: she is not Mr Salmond's proxy.

Anyone who imagines the departing First Minister will continue to run things "behind the scenes", or manipulate events from a Westminster pew, has not understood Ms Sturgeon. That person has also overlooked Mr Salmond's capacity for dispassionate judgment. He lost; he knows it. He brought Scotland closer to independence than even he, once imagined possible back in 1979, but not close enough. So a different voice is needed, another leader required. Mr Salmond did not hesitate over that.

Those with a psychological need for the status quo, like all those Labour MPs clinging as to grim death to tribal sinecures, underestimate the resonance of a cause. Ms Sturgeon defines herself, her successes and failures according to the condition of Scotland, not the weather-vanes of poll ratings. She is as much of a politician as any of them but the idea of national choice sets the bar high indeed. That's not often discussed in a branch office.

The referendum was supposed to be the big deal. If Ms Sturgeon has anything to do with it, the judgment could turn out to be premature. This isn't over. It's hardly begun.