It is usually a mug's game to read much into one poll of voting intentions, but in the case of the latest YouGov poll on independence there is no denying its significance.

YouGov is a highly reputable company that has tended to be conservative when estimating the Yes vote, so its finding that the No camp is just six points ahead of Yes excluding don't knows, compared to 22 points a month ago and 14 points two weeks ago, is important and meaningful.

Such was the poll's impact that the value of the pound dipped against the dollar and RBS shares fell. It quite clearly shows an increase in support for the cause of independence, though as with any poll, the exact extent to which Yes have closed the gap on No remains a matter of speculation.

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This may come to be regarded as a pivotal moment in the campaign. It has turned a sedate punt to the finish line into a white-knuckle race. Those both inside and outside Scotland who were keeping only half an eye on proceedings will now be giving this contest their full attention. The pro-UK campaign remains ahead, but a Yes vote now appears to be if not likely then a distinct possibility.

Why the big change? One interpretation might be that Better Together has lost ground because of a continued failure to articulate the positives of remaining in the Union. The problem was recently well illustrated by Alistair Darling, who used his opening and closing statements in last week's BBC TV debate with Alex Salmond not to lay out an appealing vision of Scotland within the UK to galvanise undecideds, but to attack the SNP on its currency policy and other matters again and again.

Better Together have an absolute duty to point out the real risks of independence but also to shout the positives of remaining in the UK. How are voters supposed to appreciate the choice before them otherwise?

At the same time, however, Yes Scotland, after accusing Better Together of being "Project Fear" for months, has been using these final weeks to engage in negative campaiging of its own, making highly disputable claims about how the increased involvement of the private sector in the NHS in England threatens NHS funding in Scotland.

Has that charge turned heads and persuaded some undecideds to back the pro-independence campaign? Perhaps. Certainly neither side can now credibly take the moral high ground when it comes to claiming to be positive.

What happens now rather depends on Better Together. It will today be wondering what it can do to take back the initiative in this campaign. Certainly, voters wish to be reassured that the pro-UK parties will deliver extensive further devolution if they vote to remain in the UK, so Better Together is likely to want to reiterate that commitment strongly and make the case that greater devolution would allow Scotland to continue to benefit from the stability and certainty of UK membership.

What this poll shows above all is just how much can change in a fortnight - and there is still a fortnight to go.