ALL eyes are on Aberdeen this week, and not for the Northern Lights. According to the electoral calendar, the SNP spring conference ought to be a simple rally ahead of the council polls in May. But the event has taken on a life of its own. Not a stall has been set up, or a lanyard hung round a delegate’s neck, yet it has already entered political history. It is Nicola Sturgeon’s big moment. Having declared a second referendum “all but inevitable”, it seems there are very few places left for the First Minister to go short of calling one.

There is some wriggle room. She could table a referendum bill at Holyrood, or request referendum powers from Westminster, neither of which would technically bind her to holding a plebiscite. But having taken both the country and her party to the brink, almost any forward step would surely feel like a point of no return. However if Theresa May has not triggered Article 50 by the conference, it could be wiser to hold fire, and give her verdict on it in the less partisan surroundings of the Scottish Parliament.

But just as a referendum looks inevitable, the SNP’s messaging is starting to break down. Andrew Wilson, chair of the SNP’s Growth Commission, this week admitted oil would not, as the party claimed in 2014, have been a “bonus” under independence but would in fact have been an integral “basis” for the economy. Some £8bn a year was “baked” into the spending plans, and was vital to keeping Scotland’s deficit at a manageable level. Without it – and North Sea income is now zero – the national accounts would be drowning in red ink.

This mea culpa is a necessary part of the SNP recasting its referendum offer. Mr Wilson said revenues should now be assumed to be nil under independence. There will be other dramatic U-turns. The 2014 mantra that Scotland could continue to share the pound despite the UK Government’s flat refusal will not fly next time. This is extremely delicate work.

Not only does the SNP have to repackage its offer, it has to explain why it was wrong the first time, while still maintaining voter trust. What was striking about Mr Wilson’s remark was not that he said it, but that SNP HQ seemed unprepared for it. When their rivals seized on the quotes to claim the SNP had been caught out in an almighty lie to the electorate, the best the party could do was accuse them of relishing the decline of the North Sea. It was a pretty shallow response to a serious charge and a profound change in the debate. John Swinney put in a spirited turn at Holyrood on the subject, but his line was equally thin tit-for-tat stuff: David Cameron told an oil whopper once too, so that cancels ours out.

In the last referendum, Alex Salmond and the Yes campaign argued they had trust on their side. They would always be first in the queue to look after Scotland. Polling found voters had a healthy mistrust of both sides, but there was a slight advantage in Mr Salmond’s favour, with Better Together’s Alistair Darling less trusted than the then First Minister.

The SNP’s shift from past arguments and embrace of new ones for independence doesn’t mean it will be automatically distrusted. But unless the transition is done well, that slim but critical edge could disappear. Unionist parties say the SNP can never be trusted again, not least because of that “once in a generation” line. This is wishful thinking. Everyone in politics has form on misleading voters – look at the broken Tory manifesto promise on National Insurance contributions. Trust is relative, not absolute. But when every vote counts, bungling the rewrite of the independence offer and risking erosion of trust is not a good start for the SNP. Before she makes history – or not – in Aberdeen, Ms Sturgeon first has to nail down the basics.