The chances of the SNP winning a majority in the Scottish Parliament could come down to nine key battleground constituencies, polling expert Sir John Curtice has said.

The Strathclyde University professor says it is “crystal clear” the SNP will remain the largest party in the next session of Holyrood and Nicola Sturgeon will continue as First Minister.

However, he said there are still many important points which remain uncertain about the election’s outcome, chiefly the question of whether the SNP will have a majority on their own or not.

Writing in The Scotsman ahead of polling day on Thursday, he said the Greens appeared to be heading for a record performance, which would ensure there is a majority of pro-independence MSPs in the next parliament.

Sir John said: “While some polls suggest that the SNP might win a majority, others have suggested that they could fall short.

“This reflects the fact that how many seats the SNP win is likely to depend on how well they do in nine knife-edge constituencies where either the Conservatives or Labour are defending a majority of five points or less.

“If the SNP were to gain six of these that could well be sufficient to deliver the party an overall majority irrespective of what happens on the list vote.

“Those polls that put the national level of SNP support at 48% or more and the Conservatives and Labour on little more than 20% imply that the swing to the nationalists since 2016 will be enough to see at least half a dozen of these crucial marginals fall into their hands.

“Those that put support for the SNP a little lower and that for the two principal opposition parties a little higher suggest that the SNP will fall short.”

Sir John stressed that these local races could look different to the national picture.

He suggested the relatively high Leave vote in the EU referendum may make it easier for the Tories to defend Galloway and West Dumfriesshire than in Eastwood – where only around a quarter voted Leave.

Meanwhile, in Dumbarton, Labour’s Jackie Baillie has a slim majority but her personal profile may be enough to ensure she can hold on, he said.

Whether or not the SNP secures an overall majority could depend on local considerations

Sir John continued: “In short, whether or not the SNP secures an overall majority could depend on local considerations in just a handful of constituencies.”

He noted the SNP were performing less strongly on the regional list vote, with the more significant challenge on the pro-independence side coming from the Greens rather than Alba.

While Labour and the Conservatives are roughly “neck and neck” in the constituency ballot, Sir John said Anas Sarwar’s party are lagging behind in the regional list vote.

Sir John said: “In truth, there is still much left for the parties to fight over in the final hours of the campaign.”