Tomorrow will see the SNP’s footsoldiers make a pilgrimage to Aberdeen for a party conference that looks set to be a gathering of considerable political significance.

On a constitutional journey marked by more than its fair share of milestone moments, it can be easy to grow weary of some of the hype surrounding such events.

But, on this occasion, the trip to the North East promises to be a first-class opportunity to take the temperature of activists and how they think the SNP leadership is doing.

An SNP supporter takes a picture at the SNP spring conference at the SECC in Glasgow.

In recent years, SNP conferences have been marked by the undivided loyalty of a grassroots’ movement united behind its common goal of Scottish independence.

This time round, however, things may well be a little different. There will be less of the euphoric, showbiz-style presentation that characterised the SNP’s astonishing surge in popularity from the ashes of independence referendum defeat.

Since those heady days, there has been an injection of realism courtesy of the complexity of Brexit and, more recently, the publication of Andrew Wilson’s Growth Commission report.

Already Mr Wilson’s document, commissioned by Nicola Sturgeon, has begun to challenge the undisputed loyalty the SNP leader once commanded from her party. After years of successfully uniting those from the right and the left under the banner of independence, some cracks are appearing.

Growth Commission is 'second biggest mistake of Nicola Sturgeon's career'

Although praised in certain quarters for pragmatic economics, those on the left are alarmed that Mr Wilson’s strategy to cut Scotland’s £13.3 billion deficit will usher in more years of economic hardship.

Mr Wilson’s 354-page tome has thus deprived the left of its vision of independence as an uplifting – if romantic – chance to break free from the shackles of austerity.

Perhaps the strength of feeling the document has aroused explains why there are no formal plans by the conference organisers to debate the Commission’s findings on the floor of the conference. Any carefully choreographed illusion of party unity would be pretty quickly shattered by an almighty stushie over what has become the key economic document in the drive for a second independence referendum. Even so, it does seem an unusual omission on the organisers’ part not to have officially set aside time to discuss such an important contribution to the debate.

The SNP say there is still a chance that a member could introduce the subject in the form of a topical resolution. But whatever happens – debate or not – the Growth Commission will be the dominating theme of Friday and Saturday’s event in the Aberdeen Exhibition and Conference Centre.

It will overshadow the widely anticipated election of Economy Secretary Keith Brown to the position of Depute Leader.

Even if the unthinkable happens and Mr Brown, the red-hot favourite to succeed Angus Robertson, is unexpectedly defeated by Cllr Chris McEleny or Julie Hepburn, the Growth Commission will still loom large over the gathering. In that regard, the liveliest session is likely to come in a fringe meeting hosted by the Institute of Economic Affairs that will actually see the document discussed. Mulling over its contents will be Kirsty Blackman MP, Joan McAlpine MSP and the former MP and economist George Kerevan. Of those three, Mr Kerevan is bound to have something interesting to say. He is one of the growing group of figures within the Yes movement who have expressed deep reservations about the Mr Wilson’s conclusions.

Writing in the National newspaper last week, Mr Kerevan said the “hairshirt approach” might satisfy the “Presbyterian souls of some of the Scottish commentariat and intelligentsia”, but not the working-class voters looking to the SNP for hope.

He said that, by trying to allay middle-class worries about an independent Scotland’s finances, the document was “in danger of robbing the next independence referendum of being a rallying cry of hope for working-class voters”.

With the stroke of his pen, Mr Kerevan aligned himself with other independence supporters on the left who have made similar disparaging arguments. With Ms Sturgeon obliged to give her full support to the document she commissioned, it will be challenging to paper over the cracks.

In the meantime, in her introduction to the conference agenda, the SNP leader promised that the weekend “marks the start of a new chapter on the road to independence”.

As she starts out on yet another road to independence, the challenge of uniting her own party is compounded by her need to convince the public at large.

Although Mr Wilson has been insistent that his document rejects austerity and represents a sensible and achievable route towards splitting the UK, its candour will make independence even more unpalatable for those who have yet to be convinced. The currency conundrum that proved so difficult for the Yes movement still exists.

Despite protestations to the contrary, a “solution” that will see the retention of the pound without control over monetary policy for a decade still leaves the SNP open to attack.

The quarter of a century Mr Wilson estimates it will take to catch up with the economic performance of other advanced, small nations may be a stimulating challenge for at least some of the converted. But it is unlikely to appeal much to die-hard No voters.

Tom Peterkin: SNP split over Growth Commission may be about to widen