THE UK’s leading polling guru has told The National what he thinks the Yes movement needs to do “above all” in order to win independence.

Professor John Curtice said that too much of the debate was about the technicalities of devolution or the process of holding a referendum – with too little attention paid to the “substance of the case”.

In order to win, Curtice said, Yes campaigners would have to “move the agenda” on to the benefits of independence.

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He told The National: “The real thing the Yes side have to do – and this is one place where Alex Salmond was spot on – they need to get the debate to be about independence. Not about tactics of independence, which is the trap the Unionists have fallen into, and not into arguments with the UK Government about process.

“What above all the SNP and the Yes movement have to do is they have to persuade people of the merits of independence. Unless they do that, arguing about the process and how you get to a referendum is frankly angels dancing on the head of a pin. It won’t matter unless you can persuade people of the substance of the case.

“There is a big debate to be had about the merits of being inside the UK and outside the EU versus inside the EU and outside the UK. This is the big debate that the Scottish National Party needs to start. The longer they spend arguing about tactics, the less likely it is they are going to make the kind of progress they need.

“If tomorrow Rishi Sunak had a Damascene conversion and said ‘Nicola, I’m terribly sorry, you’re quite right and you can have your referendum in October’. God almighty.”

The National: Rishi Sunak and Nicola Sturgeon

Curtice’s point was echoed by independence activist Jonathon Shafi, who spoke out in the wake of a poll showing independence support had dipped to 44% against 56% for the Union, with don’t knows excluded.

The full results of the Lord Ashcroft Poll put Yes on 37% and No on 48%. A total of 12% of people said they were undecided, and 3% said they would not vote.

Shafi said the results showed “partly why I think the indy movement is having the wrong conversation”.

“De facto indyref not the real debate. The whole case needs rebuilt after years of neglect,” he added.

Curtice told The National that the debate around whether or not to treat the next General Election as an independence referendum was the first time since Sturgeon had taken power that her ability to control the SNP’s “strategic direction” was “in significant doubt”.

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He said: “The opposition might be fragmented, Stewart McDonald’s saying one thing and [Angus MacNeil] is saying something different again. But to that now of course you can add the fact that it doesn’t make sense to hold either referendum, de facto or not, unless you’re ahead on the issue in the polls.”

The SNP will hold a Special Democracy Conference on March 19 to decide as a party on the next steps towards independence.

The party’s ruling National Executive Committee (NEC) has proposed a motion calling for a de facto referendum, but the Ashcroft polling published on Monday suggested that even among SNP voters this is not the favoured route (48% oppose it vs 44% who back it).

Asked if Sturgeon might be hoping that the SNP conference rejects the idea of in order to open a pathway to dropping it altogether, Curtice said: “I don’t see how that’s to her advantage because it will be interpreted both within and outside the party as evidence that she is losing command.

“The potential room for manoeuvre is I think it might be a de facto referendum on having a referendum.”

This is the NEC’s second proposed route, which will be put to SNP delegates at the March conference.

Curtice added: “If that indeed is going to be the party’s objective, then the question is … how are you going to persuade more people of the merits of independence? It still gets you back to that crucial question.”