If the Vow didn't swing the referendum, then what's the justification for further devolution?

David Cameron, Jim  Murphy, Nick Clegg, they have all assured us – the Vow has been delivered.

The only problem is, it’s not clear that anyone voted for it – at least according to a study from the University of Glasgow, suggesting that the intervention on the front page of the Daily Record did not swing the referendum vote.

The study by Ronald McDonald and Xuxin Mao, which used Google Trends data to analyse the significance of key events during the referendum campaign, says: “We find that for this final period in the referendum process that neither the Vow nor the last TV debate had any significant effect on the final voting results.*

“However, the Sep 5 You Gov Poll did have a significant positive effect on the Yes vote but no effect on information search activities.”

It adds: “Our analysis shows that the key element in pushing the Yes vote to 45% in the final lap of the referendum was the ‘grassroots effect’ of ‘Yes’ voters on swing voters.” 

The report will be seen as a blow for the SNP’s narrative, that Scots are demanding more than the powers offered in the Smith Commission.

And who knows what Lord Smith makes of it, having been tasked with bringing five political parties together to create a new constitutional settlement, in a matter of weeks, on the basis of a newspaper front page that may not have mattered anyway.

But actually it raises problems for everyone, because if the Vow did not swing the referendum vote to No, then what did?

And what is the democratic justification for further devolution?

If it had been a Yes then it is clear that Scottish independence would have political legitimacy.

But a No is a murkier choice. It could mean a vote for the status quo, or it could mean a vote for home rule, or it could mean anything in between.

Imagine, hypothetically, a voter wanted to keep the status quo. Then the three main party leaders, startled by high support for Yes, offer the Vow.

At that point, a voter who wanted the status quo would still need to vote No, as the lesser of two evils, even though it would be interpreted as tacit support for The Vow.

The argument for a third option on the ballot was rejected in negotiations over the Edinburgh Agreement, though it was clearly pretty well favoured by the population.

If it had been an option on September 18, we would know what support it had.

Instead, Scots are left guessing at what the electorate was expressing, as its sovereign will, on September 18 2014.

Scots were asked if they wanted independence. But their answer has just posed further questions.

*Note: New study released 26 March 2015, suggesting same findings but using panel surveys