Questions of independence: Why has the Yes campaign had a boost in the polls?

In short: calendar, competence, complacency.

Although it has rumbled on for two years, the referendum only shifted into top gear when the Commonwealth Games ended four weeks ago. At that point, the Yes and No camps stopped circling each other and went for the jugular, starting with the first of two TV debates between Alistair Darling and Alex Salmond on 5th August.

Press and broadcast coverage is now nearing saturation point, Yes and No stickers are proliferating on windows, cars and chests, and 18th September, the date of the referendum, has become a staple of everyday conversation. Turnout is expected to be 80 per cent or above.

With a large, diverse and highly motivated grassroots movement working the doorsteps, the Yes campaign is capitalising on this voter engagement with simple, well-timed messages: we can keep the pound, a No vote threatens the NHS, a Yes means jobs, oil and free childcare. Some of the claims are half-true at best, but they are connecting. Crucially, confidence that the economy would stay healthy under independence is increasing; In June, YouGov found economic optimists outnumbered pessimists by 49 to 27 per cent. The gap today has narrowed to 44 to 35 per cent.

The Yes campaign is also chasing every vote. Because of their sheer number, Scotland’s 1m Labour supporters are targeted relentlessly. Leaflets printed in Labour colours urge them to vote Yes to “end Tory rule forever."

Meanwhile, habitual non-voters, the so-called “missing million," are sought out in the housing schemes by far left groups such as Radical Independence and the Scottish Socialists.

In contrast, and in what may prove its undoing, the No campaign is sticking rigidly to a strategy of targeting only undecided voters. This has let the Yes campaign sweep up voters who were assumed to be on one side, but who turned out to be persuadable, especially when offered left-leaning messages on public services. Support for a Yes among Labour voters rose from 18 per cent to 30 per cent last month, YouGov found.

Better Together’s harping on the downsides of independence, particularly uncertainty over the currency, makes intellectual sense, but lacks any imagination, emotional impact or vision. The rational only takes you so far in politics. “Campaign in poetry, govern in prose,” said Mario Cuomo; the No side campaigns in statistics.

The inability of the three Unionist parties to agree which new powers should be devolved to Holyrood in the event of a No, Scotland’s stubborn Toryphobia, and a knack for gaffes such as last week’s patronising broadcast aimed at women are also causing the No side considerable grief. David Cameron would be right to be nervous.

The Yes side’s colourful bandwagon has momentum and is drawing in voters, while a flat and tired No campaign hasn’t a clue how to stop it.

Tom Gordon is Scottish Political Editor of the Sunday Herald, the only newspaper so far to declare its support for independence.