Those rather loud and distressing noises emanating from the Better Together camp in the independence referendum sound suspiciously like the gnashing of teeth. They've been evident since it became clear to us all that David Cameron would be sticking to his guns and would not be engaging in a live television debate with Alex Salmond. For, whatever angst there might have been in the Yes camp at the British prime minister's refusal to go toe to toe with Scotland's first minister, it would have been as nothing compared to the creeping sense of hysteria that slowly began to engulf the executive of the No camp. As it dawned on them that one of their own serried ranks would now have to meet Salmond in verbal combat, they all must have shivered together in the manner of men who know that one of them must walk the plank.

"I think it ought to be you Alistair; after all, you are the Scottish secretary." "No Alistair, after you; aren't you supposed to be the campaign leader?" "And what about you, Gordon, after all you were the iron chancellor, were you not?" "And what about you Jim, you and your ridiculous Irn-Bru crate?" In the end, of course, it was Alistair Darling who drew the short straw, and so on Tuesday he will step blinking into the eye of Scottish Television's cameras at Glasgow's Royal Conservatoire to be confronted by the SNP leader.

Alistair Carmichael, I fear, would never have been seen in polite society again if he were made to go 15 rounds with the first minister. Gordon Brown's ego, meanwhile, would simply never permit its master to risk a defeat by a man he considers beneath him. If Salmond brings his "A game", as they say, it should all be over quicker than an English middle order collapse.

The first minister has been largely anonymous in the independence campaign thus far. This may have been partly due to the fact that he seems to be one of those public figures for whom prolonged exposure on our television screens does no favours at all.

He is very good, but he conveys a sense of knowing that he's very good: Scottish audiences like the first but not the second. In this, he has been unfortunate. Perversely, the absence of a consistent challenge by assorted unionist leaders, both at the dispatch box and in public life, has merely served to make him look more arrogant and smug than he probably is in real life.

Quite simply, the efforts of his opponents, and especially the Labour front-bench, have been utterly lamentable in seeking to give him a good game. The majority of them are simply not good enough, though Johann Lamont has occasionally stayed the distance.

The most likely explanation for his demure approach thus far in the campaign is simply that, with a little more than six weeks until 18 September, he is being introduced to the play at a time when he can operate at full tilt. In this way, the potential for him to run out of steam or to become an overfamiliar and potentially unwelcome presence is diminished.

Darling's only hope of matching his opponent (he will never better him) during this exchange and the second one to follow lies in disrupting the flow of debate. The former chancellor is a thoroughly insipid public speaker who engenders no passion or belief in what he is saying. His answers seem learned by rote and his continual blinking as he's delivering them makes him look unconvincing, like an understudy who's just been acquainted with the script owing to the leading man being incapacitated.

At some point, I would expect Darling to attempt to shout down his opponent by constantly interrupting him, a tactic that worked well for Lamont when she encountered Nicola Sturgeon in debate earlier this year. That, though, is where the chairman, Bernard Ponsonby, must come in. Scottish political broadcasting is blessed by having several excellent journalists, of whom Ponsonby and his BBC counterpart, Brian Taylor, are the finest. Ponsonby is harder than Taylor and can skewer politicians with sinister elegance. He was the man who chased a spectral George Osborne into his people carrier last year when the chancellor refused to answer proper questions about his supposed veto on currency sharing. He'll clamp down heavily on vacillating or filibustering.

Darling has had a lacklustre independence campaign. Watching him trying to prop up Osborne's empty veto on currency union little more than a year after he himself said that it would be the best option for both countries in the event of independence was especially excruciating.

He has allowed his approach to be dictated by Better Together's dismal Project Fear strategy when he ought instead to have adopted the message of David Cameron, his Conservative ally. Near the outset of the campaign, the prime minister declared that of course an independent Scotland could be a successful small nation but that he simply felt that it would do better within the union, a perfectly reasonable and mature position.

The nationalists, though, are in no position to be overconfident about their chances even if their man gets the better of Darling on Tuesday. They are often too quick to pat themselves on the back for "awakening the country from its slumbers" during their coast to coast tour de force in the nation's town halls. This will count for nothing if it is Darling, cast in the role of Geoffrey Howe's dead sheep, who is standing under a union jack with David Cameron on 19 September.

Salmond's main challenge during this debate will not come from any deft touch or rapier thrust from his opponent. Rather, the biggest obstacle he must overcome is his own self-confidence and sense of self-satisfaction. If he does begin to eviscerate Darling early in the proceedings, he must avoid any showboating or mock-exasperation or that smirking thing that he does like the swot who knows the answer but lets the class bampots make eejits of themselves trying to answer first.

It's not difficult to descend from intellectually robust to mere rodomontade and sometimes Salmond does it, especially when he dismisses sentiments he doesn't like as "bluff and bluster".

I expect Alex Salmond to defeat Alistair Darling soundly on Tuesday night, but it would be better for him if it wasn't too soundly.