He said disagreements within the SNP over its approach to securing a Section 30 in order to hold a referendum, could stop it from the “realisation of their ambitions”.
He also said the new pro-independence parties which have recently announced they will challenge the Scottish Parliament elections next year could leave the movement as divided as the “fragmented” unionist parties, rather than winning any more MSPs.
However he warned that if the SNP was to reveal a "plan B” if the UK government continued to say no to a referendum, it would only benefit Boris Johnson.
Professor Curitce, whose comments were reported in The Courier, said: “The brutal truth, it seems to me, is that the biggest risk the SNP face to the realisation of their ambitions are their own internal divisions.
“Obviously Nicola Sturgeon will face the difficulties of the handling of the Alex Salmond affair and there is a reasonable debate to be had about what are you going to do if you get an overall majority and the UK Government does still say no.
“I suspect Sturgeon will be wise at some point to say a little bit more about that but she’s obviously determined at the moment to say, ‘I’m just not talking about independence at all’.”
This year has seen the launch of the Alliance for Independence and the Independence for Scotland parties, while controversial blogger Stuart Campbell has said he is still considering plans to launch his own Wings Over Scotland party.
Professor Curtice said he believed Nicola Sturgeon will not want to be “in hock” to MSPs from other parties and her demand for a new referendum could be “weakened” if she does not secure a majority at the Holyrood elections.
“At the moment, the opinion polls are saying you’ve never had to worry less about the need to game the system,” he said.
“For the moment, at least, the SNP are heading for a whopping great majority, anyway. Things may be different next May but right now one would say it’s just not necessary.
“The obvious risk, then, is then what the unionist side is going to make of it if there is a significant and serious list vote, particularly with the idea of putting Alex Salmond at the head of the list.”
He added: “Given where we are now in a post-coronavirus world, it seems to me that above all what you want to do, from a nationalist perspective, is maximise the chances of there being an SNP-only majority in Holyrood after next May.
“I’m assuming the SNP will say something much less circumstantial than in 2016 and say, for example, we want a referendum full stop within the next parliament, not if circumstances change.
“So if they make the same promises as in 2011 and they get the same outcome as 2011, the UK Government will be absolutely on the back foot.
“Because the problem with the UK Government’s position is that, yes, sure, you can keep on arguing that the SNP said once in a generation and that they should keep their promises but what you cannot do is bind the electorate.
“And if the electorate decide that they wish to back another referendum and they give the SNP an overall majority, then you cannot say we are going to ignore you.
“The electorate cannot be bound by the promises that were made by politicians in 2014. The electorate have the right to be fickle, even if your opponents don’t.”
He said that the SNP would not want to reveal what its “plan B" would be should Boris Johnson refuse a Section 30 order “because that potentially takes some of the pressure off the UK Government. That said, I think Sturgeon will need to give some indication that there is a plan B and maybe some indication of what it might mean. I think she would be wise, partly just to keep her troops happy, just to indicate what her alternative would be.”
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