IF the architects of the Yes campaign for Scottish independence were hoping that recent events would put rocket boosters under their cause, they will be disappointed by the latest TNS BMRB poll published in The Herald today.

The SNP has been busy recently. Having named the day for Scotland's date with destiny, Alex Salmond took to the podium at his party's spring conference to explain "the why of independence". He followed up with a series of strong attacks on the pro-UK parties over Iraq, Trident and military jobs and promised to abolish the bedroom tax in an independent Scotland. Yet a poll conducted in the immediate wake of this flurry of activity shows support for independence has fallen by three points rather than rising. And, though the percentage of voters opposing independence also fell, it was by a single point, while the "don't knows" are up four points to 19%. The bottom line is that there appears to be a fairly consistent gap of around 20% between the two sides of the debate. There is also considerably less enthusiasm for independence among women and the over-55s. That is not where the Yes campaign would want to be at this stage.

However, it would be quite wrong for anyone to assume that the independence debate is over almost before it has begun. With 18 months to run, the organisers of both campaigns are rightly wary of creating voter fatigue. Over the past six years on several occasions the yes and no votes have come within touching distance of one another in the same poll. History may suggest that the side advocating major change needs a healthy lead in the run-up to the poll but the Yes campaign has around a year to build such momentum.

It clearly has its work cut out. Has the leaking of John Swinney's Cabinet briefing, revealing private concerns about the state of the economy and affordability of pensions and benefits in an independent Scotland sown doubts about the SNP's upbeat vision? Labour's respected Frank Field, the UK Government's poverty tsar, raised similar doubts yesterday and a report from the Lords Economic Affairs Committee this week looks ready to add to them. Meanwhile the level of donations to the Better Together campaign from the business community implies that it too needs convincing of the economic arguments for independence.

Meanwhile Labour, the Liberal Democrats and the Conservatives are preparing to jointly back extra powers for Holyrood, challenging the SNP claim that a No vote is for the status quo. In national politics too the tectonic plates are shifting, making a Labour government or Labour LibDem coalition more likely post 2015, rather than the perpetual Tory rule from Westminster, as posited by the SNP.

Yet, though such factors make the hill for the Yes campaign look steeper, the campaign is only just beginning. Despite skirmishes over currency, EU membership and defence jobs, the real battle for hearts and minds has hardly begun. Much will hang on the detailed policy blueprint promised by the SNP in the autumn. If the Yes campaign has yet to make a decisive breakthrough, past history shows how much can change in a short time. As the Yes campaign will doubtless observe, ultimately there is only one poll that counts.