The launch of the "Better Together" campaign to reject outright Scottish independence has come at an interesting moment. Last week a series of polls were published which must have been troubling for Alex Salmond.
It's something that didn't get much attention in England but the polls showed that support for Scottish independence had slipped quite significantly, and that Alex Salmond's personal ratings were on the wane.
In both cases the polls bucked a trend. Salmond has remained highly popular as first minister and support for independence has been slowly but steadily rising. But in this lastest poll it suddenly fell by four points from 39% to 35%.
What's slightly baffling about the poll by IPSOS Mori Scotland is how it comes a fortnight after Salmond launched the Yes campaign. The pollsters also used the SNP's preferred question: "Do you agree that Scotland should become an independent country?", something the pollsters themselves find "problematic".
So what's happening?
The most likely explanation is that the SNP are struggling with the details of their vision for an independent Scotland, as they face increasingly detailed questions about how it might work. After acknowledging that the SNP would keep the pound, Nicola Sturgeon claimed that Scotland would have a seat on the Bank of England Monetary Policy Committee, which was widely ridiculed.
Alex Salmond has also all but admitted a highly embarrassing U-turn, suggesting an independent Scotland would seek to remain in NATO. Then the SNP was accused of a further inconsistency when the Westminster government announced contracts which would pave the way for renewing Trident. The SNP said it opposed Trident's renewal and the continued presence of "weapons of mass destruction on the Clyde". So why, in that case, U-turn on remaining in NATO, a club dominated by nuclear nations?
Another factor could be the influence of Rupert Murdoch, who has come out in favour of Scottish independence. The Murdoch brand is tainted by phone hacking and the subsequent Leveson inquiry, so having a backer like Murdoch could well be counter-productive, at least at the moment. Salmond will be hoping this becomes less of a factor as memories of the News of the World and the Leveson Inquiry recede ahead of the referendum.
Mark Diffley from Ipsos Mori Scotland points out that things are not yet disastrous for Alex Salmond. "He looked for a while relatively invincible and untouchable," he told HuffPost. "A longer-term look at his ratings suggests he's back to where he was two years ago, and that's not a bad place to be. But he's risen so high and things now appear to be on the turn. It's interesting stuff."
It doesn't mean it's plain sailing for the unionists. The campaign doesn't appear to have a position on whether Scots should consider an alternative to full independence, various models of greater devolution within the union commonly known as devomax or devoplus.
The "Better Together" campaign won't be talking about Devomax. Alastair Darling said on Monday morning: "The first question surely that we in Scotland have to answer is ‘do we want to stay in the UK or do we want to leave?’
"If we want to leave there are all sorts of consequences then," Darling claimed. "If we are going to stay in the UK then of course then you look and see whether or not there are to be additional powers for the Scottish Parliament – indeed it’s getting new tax powers from 2016 – that’s something we started and the present government have continued with.
“So I think it will be a positive campaign, but the second question issue, if you look at the deeper politics here, it’s got an awful lot to do with the fact that I don’t think the nationalists believe they can win the first question. They’re frightened of one question and that’s why they want two.”
And yet the "No" campaign's slogan is "We want the best of both worlds" - which sounds an awful lot like Devomax. So why not talk about it, when most accept it will be the likely outcome if Scots reject outright independence?
The problem for Better Together is that if he accepts he cannot win the referendum Alex Salmond will be tempted to start talking up devomax and attack the No campaign for refusing to discuss it. Better Together could quickly find that on a question of such importance those pushing the agenda need to have an answer for everything.
Then finally there's the problem of the Tories. A poll published on Monday suggested that support among Scots for staying in the union is shaken by the idea of a Tory government at Westminster. It's clear the Tories are now gearing up for a long general election campaign ahead of 2015 - the mood music from David Cameron on welfare reform is emblematic of that.
The Tories will keep their heads down during the referendum campaign and leave all the heavy lifting to Alastair Darling. But if they're making high profile announcements designed to appeal to middle England, won't Scots pick up on that and be worried for a future controlled by Etonians in London? And would the No campaign talking honestly about Devomax help to allay those fears?
They could easily find their case becomes wobbly as probing questions are asked, just as the SNP has discovered recently to its cost.