One swallow does not a summer make, as the saying goes. In politics, opinion polls are rather like swallows. So we might adapt that phrase slightly to the current situation in Scotland to say that one poll does not a political autumn make.
What matters in terms of polls is the trend, so we need to look at surveys over weeks and months to see if public opinion is really changing.
But with that caveat the YouGov survey in today’s Sun certainly shakes up the referendum campaign.
The poll suggests that the 22% gap between ‘Yes’ and ‘No’ from less than a month ago has now closed to 6%.
Among those who have decided which way they are going to vote, 53% are against independence, with 47% for it.
Which means that, if this poll is right, the ‘Yes’ side need just a 3% swing to them to win the independence referendum on 18 September.
There is no doubt that this survey is a blow to the ‘No’ campaign.
Most troubling for Better Together is that it appears to confirm that there may be a drift towards a ‘Yes’ vote in Labour-voting areas.
The Yes Scotland campaigners have always said that it is in what might be called "old Labour heartlands" that the campaign will be won or lost.
Blair Jenkins, the chief executive of YesScotland hailed the survey as a “breakthrough poll” and said his side now had the momentum in the run up to the vote.
In the USA that’s what political strategists call the ‘Big Mo’.
Mr Jenkins and the pro-independence side clearly believe they now have the ‘Big Mo’ and can build on this to overturn the apparently smaller gap between ‘Yes’ and ‘No’.
On the other side of the argument is the other Blair, Blair McDougall, the head of Better Together. He said his campaign were not complacent.
He added that what he called the “silent majority” of voters who are really ‘No’ supporters now need to “do their bit”.
For Better together these people are key. The pro-UK side is convinced many Scots who are instinctively for the Union are reluctant to say so. Hence the “silent majority” tag.
But with 16 campaigning days, including today, to go until the referendum, it will be Alex Salmond who has a spring in his step as we enter the final lap of the race.
Better Together leader Alistair Darling and the three main Unionist parties - Labour, the Tories and the Lib Dems - will, at least in private, be feeling more than a little anxious.
Today’s survey will make this evening’s STV debate - which will be shown live on ITV Border at 8pm and across the ITV network later - all the more crucial.
Yes Scotland will be represented by deputy first minister and SNP deputy leader Nicola Sturgeon MSP, Scottish Green Party co-convenor Patrick Harvie MSP, and actress and Scottish Independence Convention chair Elaine C Smith. Better Together will have Labour shadow foreign secretary Douglas Alexander MP, Scottish Conservative leader Ruth Davidson MSP, and Kezia Dugdale, Labour MSP and education spokesperson in the Scottish parliament.
Worth a watch.
Meanwhile we await the next poll with bated breath.
But if you want to know what the polling trends are up to now, the What Scotland Thinks website has all the details and analysis from the highly respected Professor John Curtice.