IT’S the economy stupid, Bill Clinton famously said. And, of course, he was right. It was people’s self-interest – how would independence affect my family and my pocket – which was the determining factor back in 2014 when the middle ground decided to stick by and large with the devil it knew rather than take a new direction.

As the former Labour chancellor Alistair Darling put it earlier this week the case for the Union was and is for many people a transactional arrangement rather than an emotional one.

Ever since the defeat for the Yes campaign four years ago there have been suggestions that the SNP has never really undertaken a full post-mortem on why it lost the economic case to the Unionists.

READ MORE: SNP's new report on independence sets out case for 'economic renaissance'

Now the nation is about to see its renewed arguments for a Scottish fiscal future outwith the United Kingdom.

Nicola Sturgeon’s words ahead of publication are telling when she talks of ambition and hope over the “despair of Brexit”.

In one regard, it could be argued that given the uncertainty and, for some, the shambles of the UK Government’s approach to EU withdrawal there may never be a better time for the First Minister and her colleagues to renew the case for a different path.

Ms Sturgeon is undoubtedly right to accentuate the positive. While Project Fear no doubt won in 2014 and emboldened David Cameron to hold another poll two years later, it failed in 2016 and in so doing destroyed his political career. Yet politics is never straightforward. With a third of Nationalist voters backing Brexit and the polls staying roughly the same in terms of Yes and No, there are dangers ahead for Ms Sturgeon.

There may be major uncertainties for Theresa May ahead on Brexit but there are just as big ones for the FM.

Yesterday, Mark Carney intervened on the old chestnut about a currency union, something the SNP leadership argued for in 2014, but was refused by the then Lib-Con Coalition.

The Governor of the Bank of England repeated his assertion that such an arrangement would involve “sharing sovereignty”; in other words, an independent Scotland would have to decide on fiscal matters alongside its much bigger and more powerful neighbour, the UK.

He suggested a currency union was economically possible but whether or not it was politically desirable was up to the politicians not him.

READ MORE: SNP's new report on independence sets out case for 'economic renaissance'

Some might have interpreted his words as a subtle shift towards the SNP’s position; that a currency union which was unfeasible in 2014, is now feasible in 2018.

But it takes two to tango and were there another referendum, no doubt Philip Hammond would be saying exactly what George Osborne said four years ago: no thanks.