In the turbid backwaters of social media, as in the media generally, there is no shortage of theories to explain what is going on in Scottish politics.

Often enough the chatter sounds like a blindfolded man encountering an elephant for the first time. It's big, it's huge. But what is it exactly?

If descriptions come from the south they tend to be tinged with bafflement. What are those Scots playing at? What do they hope to achieve? The word employed increasingly is "illogical". It's the polite way of saying that the forever turbulent folk beyond Berwick have lost their wits.

A variant sustains Unionist diehards in these parts. The words they favour are "cult" and "dupes". Why has the Scottish National Party built a massive and apparently impregnable lead in opinion surveys? Because, comes the reply, its supporters are the political equivalent of the Moonies; because they are ill-educated or none too bright; because they have been lied to time and again.

It's a complicated yet crude way to explain away the collapse of three Westminster parties. It's not, at first sight, the perfect formula for a hearts-and-minds campaign. A few Tories aside, no one talked like this was when Labour was picking up 42 per cent of the Scottish vote in the 2010 election. Hysterical rancour is the language of the lost cause.

If the SNP has 46 per cent of voting intentions, according to yesterday's What Scotland Thinks/ScotCen poll of polls, the evidence says a vast shift in allegiances has taken place. Every survey since the referendum is confirmed. Nothing attempted since September by Unionist parties, and by Labour in particular, has worked. Given a uniform swing, the poll of polls says Labour will drop from 41 seats to 10, the Liberal Democrats from 11 to just one.

But who believes in uniform swings? The health warning attached to all comment says you have to bear in mind history, local circumstances, incumbency, and the effort a party is prepared to expend on a constituency. Generally, it's sound advice. It also happens to be advice shredded by Lord Ashcroft's recent polling of Scottish constituencies. The movement detected was close to uniform.

It did not, and does not, resemble an aberration. For one thing, support for the SNP is entrenched. The numbers won't shift; blandishments won't wash; arguments produced with triumphant yelps - Government Expenditure and Revenue Scotland (Gers) figures, the oil price, Ed Miliband's "position" - are brushed aside. If anything - the puzzle within the puzzle for Unionism - these seem only to harden attitudes. Forty six per cent of voters have seen and heard it all before.

A referendum No vote was supposed to end all of this. That's why the SNP's opponents are so baffled, so furious. "You lost, get over it and move on," came the instruction on September 19. That was naÃ¯ve. For one thing, Better Together was meant to secure at least a 60-40 win. Its more voluble backers expected better than that. In the aftermath, they didn't stop to wonder what 44.7 per cent would do with a new sense of political engagement.

So what is going on? Let's suggest that Jim Murphy rebranding himself as the patriot's patriot - latest hashtag @JimForScotland - doesn't exactly go to the heart of the matter. The fact that the oil price is in one of its troughs has not sent SNP supporters reeling. Using Gers for another attempt to demonstrate that Scotland is too small and weak even to handle "devo-max" is, demonstrably, counter-productive. The refutations so appealing to those who think they know better than the herd are being tossed aside.

Treating voters as a herd explains a few things. Realisation has been growing among voters, steadily and surely, for generations. The occasional prod when an election is in sight no longer does the trick. This applies particularly, by common consent, to Labour.

It has not distinguished itself by its leadership at Holyrood. It sided with Conservatives in the referendum. Its response to deficit mania is austerity with a happy face. Its priority seems, not for the first time, to be its own survival and a Labour government at Westminster whose sole virtue is that it is not, according to the label, Tory.

The cry of "Vote Labour and Keep the Tories Out" did no damned good in 2010. Its 2015 equivalent - "Vote SNP, Get Tories" - therefore loses all meaning. The idea that "you only get a Labour government if you vote Labour" is as fatuous as the claim that the biggest party in the Commons forms a government. Those SNP supporters want a non-Tory administration in Westminster: there's a difference. The old binary logic no longer applies.

Westminster itself is another well-described factor. Only those trapped in that bubble by the Thames talk about disgust with the old main parties as "anti-politics". In their confusion, they suggest that anyone who fails to vote Labour or Tory (or even Lib Dem) has made an illegitimate choice. Recent tantrums in the London press bear this out. When arguments fail, xenophobia will do.

Reality is captured better by the fate of the LibDems. The What Scotland Thinks/ScotCen poll of polls has them on just four per cent, perilously close to margin-of-error territory, and a huge collapse from the 19 per cent recorded in 2010. Labour is far from alone in suffering a mass defection to the SNP. What's remarkable is that Nick Clegg, Alistair Carmichael and their party expected any better after their behaviour in government and their antics in the referendum.

If you believe Labour, meanwhile, Scots can vote as they please, but they will be obliged to support Mr Miliband's "progressive policies" if the Conservatives are ousted. Would the SNP ever dare side with the Tories? It is, first, another blundering way of saying that Scottish choices can never count for much. Secondly, it forgets the Fixed-term Parliaments Act. Above all, intentionally no doubt, it ignores how power is wielded in the Commons. Which SNP motions would Labour vote against?

This week's Survation/Daily Record survey was in line with the poll of polls, but granted the SNP still more seats - fully 53 - when a uniform swing was applied. The tabloid offered another detail, however, to suggest that the SNP phenomenon is no passing eclipse. If Labour, Tories and Lib Dems expect a hellish year in 2015, the year after will bring no relief: 50 per cent for the SNP in the constituency vote, 39 per cent on the regional list.

It suggests that voters understand their electoral system perfectly well and are prepared to exploit it to the full, first to keep the SNP in power at Holyrood, secondly to support other parties active in the Yes campaign, the Scottish Greens above all. And in the context of Scottish elections, lest we forget, Labour cannot pass off "Vote SNP/Green Get Tories" as any sort of argument.

The second referendum, when it comes, will have this question in common with the first: why do so many Scots want self-determination? Because, in its political behaviour, Scotland bears no resemblance to the other parts of these islands. That, too, is a matter of choice.