The Herald. August 20, 2014.

You wouldn't think it from their studied silence, but the weekend's opinion polls must have induced some puzzlement among those on the No side in the independence argument. Something went wrong with the script.

After all, the first of the great and allegedly decisive TV debates between Alex Salmond and Alistair Darling was judged on the night to have done the First Minister no end of harm. He lost, said the scorecards and snap surveys. If an increase in support for Yes is the price he has to pay, Mr Salmond can probably live with that.

You can bet he can also cope with another conclusion available from the latest polls. His failure to address the currency question to the satisfaction of Unionists does not seem to have caused too many ordinary voters to recoil in fear, outrage and contempt. It was Better Together, though still with a commanding lead, that lost ground.

Perhaps the lesson of Cleggmania has not been learned, or perhaps it is being quietly ignored. The fact remains that a flurry of “approval” for the Liberal Democrat leader during televised debates in the 2010 United Kingdom elections did not transform his party's fortunes. Their vote increased marginally, but they lost five seats. These TV rituals, beloved of journalists, are not conclusive.

So is the currency issue irrelevant to Scotland's discussion? Not exactly. If No remains in the lead, as the pollsters say, then you can presume that a majority haven't bought Mr Salmond's arguments. Equally, the movement in opinion towards Yes reveals a growing group who are not fixated on the First Minister's failure to alphabetise the numerous available choices for organising a currency. With independence at stake, they're not that fussed.

There must also be a good, alternative possibility that such voters have said, in effect, that currency matters, but not that much. The more they hear of the varieties of choices made by countries around the world, the more they're liable to wonder what Unionist intransigence really means. George Osborne's “intervention” cost Better Together support. If polls and pundits can both be believed, Mr Darling won an argument, yet lost – or failed to convince – potential supporters.

Currency was supposed to be the killer blow for the No camp. At the first attempt, the Westminster parties, united in obduracy, were supposed to scare us into compliance when they ruled out any possibility of a sterling union. Then Mr Darling and his allies were supposed to expose Mr Salmond as a man who had not bothered to think things through, who had no answers when confronted with political and economic realities. As things stand, neither tactic has done the trick.

Was that ever likely? Part of an answer can be had in the straightforward disagreement between Crawford Beveridge and Jack Perry, both previous heads of Scottish Enterprise. The former says that a currency union would be in the best interests of Scotland and the residual UK; the latter asserts that it just wouldn't work. Both men come to the argument with knowledge and expertise. Both ought to have a fair idea of what they are talking about. Yet their opinions are diametrically opposed.

Perhaps that's because the issue of currency is, like so much else in the independence debate, a matter of opinion. It might be opinion supported by evidence and intellectual rigour; it might be bluster. But amid the persistent demand for “facts”, the one simple fact is that Mr Beveridge and Mr Perry personify the problem for anyone who wants those vaunted cast-iron guarantees.

When he analysed the currency union hypothesis, Mark Carney, Governor of the Bank of England, set out the difficulties as he saw them – but he certainly did not say that the thing could never work. He noted specifically that there would have to be a loss of sovereignty for Scotland. Mr Salmond did not demur seriously, but argued – as he still argues – that the gains for all concerned outweighed that objection.

Some voters find this sort of thing infuriating, and you can hardly blame them. Better Together wants to tell these people that such “uncertainty” would be eradicated with a simple No vote. But for that to be true the future policies of the Westminster parties would have to be set in stone, by some magic, and their fortunes decreed for good and all. If that can't be done, there's plenty of uncertainty ahead thanks to the Unionist parties.

For the moment, the polls say the currency is not the deal-breaker Better Together would have us believe. The Yes vote is increasing, even if the No side retains a lead. Yet in the aftermath of the TV debate Mr Darling was acclaimed precisely because of his attack on the sterling union proposal. We should judge that gambit by results.

We should also be a little more sceptical about these set-piece TV debates. Viewers might enjoy a good scrap. They might, possibly, be given pause for thought. But their real thinking isn't done while they're confusing two politicians with a pair of boxers. It is patronising to believe otherwise. “Perceptions” are not the beginning and end of politics.

Interviewed on Radio Scotland, meanwhile, Mr Salmond appears to have yielded a little ground by declaring that Scotland could retain the pound without a formal currency union for a “transitional” period. He has said that option was “viable”, but not preferable. Better Together are happy to hear that sort of talk. What does the First Minister mean? Membership of the eurozone? An independent currency?

Mr Salmond has said this sort of thing before, of course, while outlining the conclusions of the Fiscal Commission. He has also stated his preference repeatedly. But “transitional” might be a more interesting word than Better Together have yet understood. Sterlingisation, as it is called, could as well apply only until a Westminster government saw sense, or until an independent parliament was elected to make a choice free of the referendum ferment. Likely or unlikely, these are not impossible ideas.

You won't hear such a thing said in a TV set-to, of course. That's one problem with such affairs. Had a matter of opinion been settled differently within the Labour leadership during the Blair-Brown years, Mr Darling could now be explaining why he helped to take the UK into the euro, much as Mr Salmond is questioned about his former preference for that currency.

There are plenty of good reasons why voters should care about the sterling issue, and solid reasons why they might not. Despite their manifold implications for daily life, currency arrangements can sound like an abstraction. The arguments – think only of a dire word such as sterlingisation – can seem esoteric, technical, perhaps even an irrelevance. Better Together has laboured the technicalities and too often overlooked the implications.

It's just as likely that a growing number of voters have taken Mr Salmond's point: if a currency union makes sense and is not, in fact, impossible, what does that say about those who oppose the idea? Staged adversarial combat under the TV studio lights has failed to make the question disappear. There is not a lot Unionists can do about that.