Unionists need more than fear and mumbo-jumbo

The man who promised voters a referendum on Europe, and then reneged, probably doesn't count as an expert in these affairs. For him, that hardly matters. There are waters to be muddied and political games to be played. His game plan is transparent, though.

Start with the elementary stuff. Scotland and Britain are well-used to referendums. We now know we are to have the independence referendum, on Mr Salmond's timetable, in autumn 2014. We've had referendums for years, whether at the level of local government or touching on the future of a nation. We had one not so long ago on voting reform, a proposal disliked even by those obliged to back it.

Mr Cameron granted that one because it suited him: he knew he would win. He raised no arguments, as I recall, over the principle of referendums. These days they are part of the British system: if an issue matters, ask the people.

Why the feigned fear, then, over a mere advisory plebiscite on Scottish independence?

A "constitutional matter", they say, and the constitution is reserved to Westminster, not Holyrood. The second part of the statement is true, for what it's worth. But since Britain's constitution is, famously, unwritten, it is hard to say which doctrine is an obstacle to asking the people's opinion – "advisory" – on an idea.

So Michael Moore, Scottish Secretary, told us nothing new yesterday when he said that constitutional affairs are Westminster's business. Holyrood cannot bind the senior legislature. The point is the fact does not define what the Edinburgh parliament can do.

Nevertheless, that's where the fearsome "legal challenge" comes in. Someone – not a Tory Unionist, by any chance? – could attempt to prevent Holyrood from passing a referendum bill, or prevent a referendum from being held. That someone would do the Union no favours, but never mind.

Better, says the Coalition, that we do the constitutionally proper thing and transfer powers for a binding poll temporarily from London to Edinburgh. We will do so happily – for a price. Question: given the status of Holyrood and its elections within the British system, is that constitutionally proper behaviour? Perhaps it merits "legal challenge".

It's harder still to identify the doctrinal lore that allows two important questions to be asked – independence yes or no – but bars a third, one arguably representing the sort of compromise British politicians claim to love. That would be maximum devolution, so called, or a semi-federal solution that would give most powers to Holyrood save the big, British ones. Isn't that Lib Dem policy?

Mr Cameron is against the third question, he says, because he seeks "clarity". This was also the reason given for hurrying the referendum along, and – the opening gambit – having the process concluded within 18 months.

You could applaud the devotion to clear, speedy outcomes, if you like. You could also say that Mr Cameron wanted the vote done and dusted before Scots so detest his Coalition they turn to anyone – possibly Alex Salmond by name – offering an alternative.

The Prime Minister wouldn't put it that way. He says haste is essential because of "uncertainty" among big international firms liable to plant outposts in Scotland. He has the word of his Chancellor, George Osborne, for this. Yet while SNP Ministers give chapter and verse on inward investment decisions, Mr Osborne can't name a single company paralysed by noises from Scotland.

All of this is typical Cameron: it looks clever and unravels at the touch. The legal challenge argument is specious. The pure constitutional argument is dubious, and involves a can of worms. The economic argument is nonsensical.

The voting age argument is a deliberate diversion. The political argument – didn't we just have an election to prove the point? – is utterly self-defeating.

Mr Salmond need merely bide his time. What can Mr Cameron do next? Force his own referendum on the parliament of Scotland?

Politically, that would fall short of genius. Could the Prime Minister then seek to prevent the First Minister keeping an election promise of a plebiscite? You would begin to doubt Mr Cameron's sanity, far less his intelligence.

He cannot touch the SNP's legislative programme: that's where the SNP's referendum pledge lies. He can invoke nebulous constitutional difficulties, but that's hugely risky: his side would probably lose any argument over an advisory poll, legally and – the more important part – politically. It's all political: that much is also elementary. Every other argument is therefore a distraction, and comes down to this: parties that lost last May's Scottish election are seeking any means available to reverse a decision made then by the voters. A lot of those voters won't like that.

Mr Salmond has a couple of political problems of his own. One is historic and obvious. The SNP leader lives in the belief that one day soon majority opinion will move in his direction. Where the pure question of independence is concerned, history, sadly, says otherwise.

Mr Cameron's antics might do the trick: they will certainly be worth votes for Nationalism. But enough votes? And will there still be sufficient of those votes some 33 months from now if the SNP makes a few political mistakes of its own?

I fall between two camps. Which is to say, Mr Salmond should insist on a referendum on his own terms, but get on with it. Anecdotally, people are getting tired of his insistence that only one date will do. They are beginning to feel a little manipulated. They care for that almost as much as they care for Mr Cameron's bullying.

For all that, when compared with the parties of Union, Nationalism has few problems and most of the advantages. The opponents of independence have to make their case: it's as simple as that. No more scaremongering, no more tinkering with rules or constitutional mumbo-jumbo.

At this rate, they'll get their message through at about the time the high-speed rail link – a British project, apparently – reaches Scotland. By then, one cancellation will have been announced.