ONE poll does not a summer make.

But the Panelbase survey we report today is not alone in indicating a sharp narrowing of the gap between Yes and No in the independence referendum.

A poll by Survation last week made similar findings, and, like Panelbase, recorded its highest support yet for Yes.

Neither on its own offers a definitive snapshot of a diverse electorate as it wrestles with a decision without parallel in Scottish history.

However, taken as a pair - and there were reports last night of movement towards Yes in a third opinion poll - it looks as is something is afoot.

After weeks in which it appeared stalled, despite a lift early in the year, it seems momentum is returning to the Yes campaign. If that is the case - and it may require a few more polls to confirm this - it is to be welcomed.

The Better Together campaign, which dismisses any shifts against it as "wavy lines" in the data, looks increasingly desperate.

More and more, in the manner of someone who swears he was kidnapped by aliens, they insist they have just witnessed a game-changer. George Osborne refusing to share the pound. Promises of more powers for Holyrood from the No parties. President Barack Obama's hat tip to the union.

Each a guaranteed, cast-iron game-changer. Until each turned out to be no such thing.

JK Rowling donating £1 million to Better Together and Pope Francis being ambiguous are but the latest examples; we await next week's game-changers with interest.

Of course, Obama is at liberty to enter the referendum debate. And it is useful to know how other nations view the prospect of an independent Scotland.

But it also useful to remember that America, and all nations, would adjust to the reality of an independent Scotland should it come to pass.

Likewise, Rowling was entitled to make her written and cash contributions. Her essay on why she was supporting the Union was elegant and thoughtful, and many of the social media attacks on her were inexcusable.

But the key aspect of the contributions so far has been their impotence. The No campaign's artillery isn't working. However they tweak their message - turning their slogan to "No Thanks" for instance - it remains negative and dispiriting. Voters are uninspired and turn away.

Labour, with a nervous eye on the general election, has realised this, and the party is sending out senior figures to shore up their support.

But after two years of campaigning, Better Together still struggles to articulate a winning case for keeping the Union over independence.

If this goes on much longer, even Better Together won't be able to escape the obvious conclusion: that a winning case doesn't exist.