LAST week, Alex Salmond stood accused of jiggery pokery, collusion and political manipulation over his offer to include a second, "devo max" question in the independence referendum.

The Scottish Affairs Select Committee in Westminster declared that Salmond only wants this as "an insurance policy against the verdict of the Scottish electorate".

The leader of the Scottish Liberal Democrats, Willie Rennie, then accused Salmond of using the Scottish Council for Voluntary Organisations as a "front organisation", after a leaked email suggested that the SNP leader's aides were trying to prompt the council's leader, Martin Sime, into coming up with the wording of a second question. With support for independence falling, Salmond is, we are told, desperately looking for a way to snatch a kind of victory from the jaws of defeat by ensuring that he gets his "second-best" option on the ballot paper.

Mind you, I'm not sure this is what the Yes campaign believe is happening. It may surprise you to learn that leading figures in the independence movement are privately expecting, indeed banking, on there being only one question. The trouble with the second question on devo max is that a lot of Scottish nationalists think, and have always thought, that it is a very bad idea. This is because it will all but guarantee that independence loses, since the vast majority of Scottish voters favour a parliament with greater economic powers. So why hold a referendum that you can't win?

There has been a great deal of activity on the referendum issue, in Westminster and Edinburgh, since the former BBC news executive, Blair Jenkins, took over the Yes campaign in June. David Cameron has insisted on a deal being struck by October 2012 to allow the referendum to be held in October 2014. This is because a so-called section 30 order needs to be put before Westminster, effectively giving the legal power to Holyrood to hold a binding referendum on independence. As things stand, the Scottish Parliament has no powers over the constitution, and therefore cannot stage a binding referendum on its own authority.

However, to get the Section 30 order, Cameron has insisted on a single question, and my understanding is that this has more or less been agreed. The deal would be that the Scottish Government will accept a single question and give the UK Electoral Commission a say on the wording of it. In return, the SNP's 2014 referendum timetable will be accepted and 16 and 17-year-olds will get to vote. This arrangement would allow both sides to claim victory in the constitutional phoney war that has been raging for the last two years. It isn't signed off yet, but from my soundings this is the most likely outcome.

Humiliation for Salmond? Not necessarily; the FM has always said that a single question was his preference. However, he wanted to avoid the charge that he was excluding non-nationalists from the referendum process and has said from the start that, if the supporters of devolution max get their act together, he would support their option appearing on the ballot paper.

However, there is as yet no sign that "civic Scotland" – made up of the various voluntary organisations, trades unions, churches etc – has come up with an agreed second question, and time is running out. As the Scottish Affairs Committee said last week, there is no settled understanding of what "devolution max" means. For some it is full-blown federalism; for others it is fiscal autonomy; for others still it is just the Scottish Parliament with a few more tax powers. It was always going to be hard to pin this one down.

The Yes campaign will now turn its attention to persuading the "disenfranchised middle" that, in the absence of their preferred option, they should vote Yes to independence. It will try to persuade waverers that they will not be voting to leave the UK or breaking up Britain by saying Yes to independence. Rather, they will be voting for a new, improved UK and will still be able to call themselves "British". The Queen, the pound, the Bank of England, NHS etc will all remain. It is new wine in old bottles. The more things change the more they will remain the same. The voting public may not buy this, but that's what they will be sold.

The problem for the No campaign, or "Better Together" as it is called, is that they're now backed into a corner. Having spent the last two years arguing against a second question, they are left trying to defend the indefensible: excluding the constitutional option that is favoured by the vast majority of Scots voters who support neither full independence nor the status quo.

Historians will puzzle over how the Unionists got themselves into this position – indeed some are doing so right now. Surely, Unionists should have been insisting on a second question in order to marginalise independence. By rejecting it out of hand, they not only look undemocratic, they risk maximising the vote for independence. The SNP need only win the support of a few thousand waverers to get within striking distance of a Yes.

It is impossible to say how many Scots will be minded to vote for independence out of frustration that they have been denied a vote on devolution max. But there will be some, to my certain knowledge – especially among Liberal Democrat voters, who are mystified at why their party, which has been committed to federalism for over 100 years, is so determined to ensure that the Scots have no chance to vote for it.

Now, I'm not saying that Salmond has planned this all along. No-one, not even his closest supporters, fully understands the thinking of the First Minister, who is a law unto himself. But the FM must have known that, by proposing the second question, he all but ensured that Labour Unionists would reject it, on the grounds that anything he proposes must be a Nat plot.

Most Labour MPs believe that by forcing him to accept a single question they will shoot Salmond's fox, destroy his morale, undermine his strength in the country. Give him a "bloody nose" and kill nationalism stone dead. I wouldn't bet on it.

With a single question, the likelihood is that independence will lose, but not lose by a massive margin – perhaps 45% Yes to 55% No. That will be a setback for Salmond, of course, but it doesn't mean that the SNP will be out of contention at Holyrood. He will go into the 2016 election calling on Scots to vote SNP to ensure that the Unionist parties adhere to those promises made by David Cameron and Alistair Darling of more power for Holyrood provided Scots vote No.

The SNP was not elected in the first place because of its policy on independence, but in spite of it. And Salmond's landslide victory in 2011 was a verdict on the performance of the minority administration and the feebleness of the Labour alternative. That hasn't changed.

And anyway, I wouldn't write off the independence vote. Strange things can happen in a fast-moving campaign, and I wouldn't rule out contrarian Scots voting Yes to independence to get a better devolution.