Scotland’s on a knife-edge. Like all referendum-watchers at the Edinburgh Festival I grabbed a ticket for The Pitiless Storm, a drama about independence, which attracts big crowds every lunchtime at the Assembly Rooms.

The play draws its inspiration from the passion and fury of Red Clydeside. David Hayman, an actor and lifelong leftie, plays a Glaswegian trade unionist who reflects on the troubles of Scottish socialism as the referendum approaches. Some of his rhetoric captures the best of the independence movement. ‘We’re not leaving the union, we’re joining the world.’ And he flavours his optimism with a dash of local irony. ‘We don’t know what the weather’s going to be like in half an hour, let alone what kind of country we could be in ten years’ time.’ But he also indulges in self-pitying nostalgia. He sees independence as a rite of exoneration and atonement, a chance for Scotland to acquit itself of its involvement in the Blair government, and in the subsequent policies of the coalition. All the blunders and compromises of the past — from the Iraq war to the bedroom tax — will be purged in the fires of liberation.

The Edinburgh audience seemed to tolerate and perhaps even to endorse this misty-eyed revisionism. After the show, David Hayman invited questions from the floor, and the first contribution came from an Englishwoman who spoke in a jaunty Radio 4 accent. ‘Britain will be sorely diminished if you leave,’ she declared, as if opening a fête. ‘Please don’t go.’ The audience, rather than hooting with derision, broke into warm and prolonged applause. Then a hoary old Scots Nat climbed to his feet. ‘The yes campaign has made the better arguments…’ he began. He was stopped in his tracks. ‘But we’ll lose the vote.’ This interruption came not from the stalls but from the stage. It was David Hayman himself, admitting defeat in front of a thousand of his compatriots.

In the New Town, I visited the yes campaign’s headquarters, which occupies a beautiful suite of rooms on North St Andrew Street. ‘Register to help,’ said the poster outside. ‘Collect campaign materials.’ In the corridor there were tables loaded with stickers and leaflets. Plastic buckets overflowed with ‘Yes Scotland’ badges. The place was deserted. A door creaked open and a nice old chap with a white moustache bustled into view. ‘All alone?’ I asked. He explained that the front-line troops were out on the streets whipping the populace into ecstasies of patriotic defiance. ‘And who are you, by the way?’ he asked. ‘Just a journalist.’ He folded his arms across his chest. ‘Then I can’t tell you anything.’ This seemed a curious opportunity to pass up. I was quite ready to annotate and publicise whatever propaganda he cared to feed me: the last-minute surge; the rising support from the middle classes; the rock-solid pensioner vote; the thirst for change across the Highlands; the rebellious fervour of the young; the toxic negativity of the no campaign; the deadly impact of Alistair Darling’s scrubbing-brush eyebrows; the cheerful rivalry between Glasgow’s foundries as they compete for the honour of casting a celebratory bronze statue of Alex Salmond smirking over a prone and whimpering David Cameron. But instead he exuded suspicion and embarrassment. ‘Feeling confident?’ I asked. He gazed downwards and moved his hand to left and right as if trying to put an old banger into gear. ‘Well, it’s a race. But I think we’re coming up the home stretch now.’ I took a badge and pinned it to my lapel as I left. I felt sorry for him.

The yes campaign is in trouble because its two secret weapons — Alex Salmond and the youth vote — have misfired. Salmond was supposed to be the redeeming angel whose sword would slay the arrogant plotters of Westminster. And behind him stood an army of juvenile hotheads with nothing to lose and everything to gain from a year-zero insurrection.

But nobody consulted them first. The Royal Mile teems with youngsters handing out leaflets for shows, and each time I accepted a flyer I asked for a referendum forecast. Here’s what I heard. ‘I’m voting no. Is that bad?’ ‘Salmond’s an arse.’ ‘I like it the way it is.’ ‘The currency’s a problem.’ ‘Salmond has no answers.’ ‘What’s going to happen about the EU?’ The currency issue recurred constantly. A lad in his early twenties told me he wished fervently that his generation had been able to deliver independence, ‘but it won’t happen’. ‘Why?’ ‘There’s no more oil.’ ‘Salmond says there is.’ ‘Well, yeah, he would…’

Mistrust of Salmond has risen to the point where he’s become a liability to his own campaign. The Scots have grown tired of his jowly smirk on their TV screens. A fringe comedian, Vladimir McTavish, gets a big laugh from this gag. ‘People ask the question, “What if Alex Salmond fell under a bus?” Well, Midlothian buses today issued a statement confirming that “no vehicle in our current fleet is strong enough to withstand such an impact”.’

Only in Scotland do you realise how well Cameron’s indifference to the campaign has played out. The SNP had hoped all along for a clumsy intervention from No. 10 that would restore Salmond’s position as a glamorous outlaw opposed to London’s evil schemers. By keeping quiet, Cameron has turned Salmond into the very thing he once opposed. The First Minister represents authority. He is now a vested interest. He has become the self-serving power base that seeks nothing but its own survival.

His supporters exist, if you can find them. On North Bridge I was accosted by a friendly old chap inviting passers-by to take a ‘Free Stress Test’. ‘Has Alex Salmond tried one?’ I asked. ‘He’s not been along this way yet.’ I followed the stress expert into an office where he seated me beside an oscilloscope wired up to two metal cylinders. I grasped one in each hand. ‘Concentrate on something that’s on your mind.’ I did so. The needle leapt to the maximum. ‘What were you thinking of?’ he asked. ‘Alex Salmond. A smart politician but he’s heading for the biggest disappointment of his life.’ This seemed to stir the old guy’s memories. Last time, he said, in 1979, Scotland was robbed of devolution by James Callaghan and his ‘corrupt tactics’. And now? ‘Salmond’s being very canny about it, very canny about it,’ he said darkly, as if the SNP’s faltering strategy were a brilliant prelude to a last-minute ambush and victory.

He was the only Scot I met who believed the yes campaign would win. He was also, I should add, a devotee of L. Ron Hubbard.