John Swinney is “not as unpopular” as Humza Yousaf, Professor Sir John Curtice has said.

However, the polling guru said the First Minister was still “not in the same league as Nicola Sturgeon”.

Speaking at an event organised by the Fraser of Allander Institute, the psephologist also suggested Liz Truss was responsible for killing off hopes of another independence referendum and claimed voters were "finally" taking the SNP's record in government into account when decided who to vote for.

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He also said the strength of Labour's messaging, together with the “worries and doubts” about the SNP, could be impacting on support for Mr Swinney.

Mr Swinney is currently in Germany, where is due to attend the opening match of the Euro 2024 finals.

Ahead of the game he met with fans at Marienplatz square, Munich.

Sir John told the event that the “constitutional question is still absolutely fundamental for unionist voters”.

Explaining why support for the SNP is down while pro-independence sentiment has remained broadly unchanged, he said: “For those on the Yes side of the argument, their worries and doubts about the SNP and also Labour’s appeal, ‘vote for us to get rid of the Tories’, that appeal caused the SNP a lot of difficulties.”

(Image: PA)

Support for the SNP was just below the level of 45% it achieved in the 2019 general election when Ms Sturgeon announced she was stepping down.

However, by the time the party's bruising leadership contest was over, and Mr Yousaf replaced her, that support had fallen to 38%.

Sir John said: “That leadership contest, both in terms of what happened during that campaign itself in the divisions it exposed and the person who emerged as the winner, was bad news for the SNP.”

He added that “maybe John Swinney has been able to steady the ship of decline”, but there has not yet been “any significant sign of SNP progress and that is potentially making things difficult for them”.

Sir John continued: “The reason why this has happened is all to do with people’s perceptions of the SNP and nothing at all to do with attitudes to independence, which have basically flatlined.

“We still are in a position where this country is divided almost down the middle on the constitutional question, with just under half of people saying they would vote Yes in an independence referendum.

“What obviously therefore is happening is support for the SNP amongst people who would vote Yes has gone down.”

He also said the leadership contest last year means the SNP is “now regarded as divided” by some voters.

Sir John said: “People no longer thought of the Scottish National Party as being united, but rather as a party that is divided, and voters tend not to vote for divided parties.”

The academic suggested voters were now “finally taking into account their perceptions of the SNP’s record in Government.”

He said analysis of the polling data shows “people who evaluate the NHS less well are less willing to vote for the SNP again”.

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Sir John went on to say that Ms Truss may have ensured there is not another referendum on independence in the coming years.

He said the SNP using political “leverage” in a hung parliament with Labour in minority administration had “always been where the next referendum was going to come from, at least in the short-term”.

But he said the dip in Tory support during Ms Truss’s short spell as Prime Minister had “knocked another six points off the Conservatives in six weeks”.

“The Conservatives have never succeeded in recovering this position,” Sir John said.

“It’s that event which has opened up the prospect of a majority Labour government, and therefore the prospect that we will have another government that can say ‘we’re terribly sorry, we’re not going to have another referendum’.

“I think there is now probably one thing we can say that Liz Truss’s brief tenure in office achieved, at least as far as the medium future is concerned, was to guarantee the future of the Union.”