THE seat that includes Holyrood, Edinburgh Central is also home to the hottest fight to get into it.

Labour-held for three terms, then gained by the SNP in 2011, it was the scene of a sensational upset at the last election, when Ruth Davidson came from fourth place to snatch it by 610 votes.

The SNP have been seething ever since. Often at each other.

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After Ms Davidson quit as Scottish Tory leader in 2019 and reset her satnav for the House of Lords, the looming vacancy triggered an almighty fight for the SNP candidacy here.

Dethroned as the party's Westminster leader by Douglas Ross in 2017, former Moray MP Angus Robertson applied, as did Edinburgh South West MP Joanna Cherry.

With Mr Robertson old pals with Nicola Sturgeon, and Ms Cherry close to Alex Salmond, it was seen as a duel between the party's rival camps.

The SNP hierarchy then coincidentally changed the rules to make it harder for serving MPs to switch to Holyrood, and a furious Ms Cherry withdrew amid claims of a stitch-up.

Mr Robertson, tipped as Ms Sturgeon's successor, is now trying to show all the grief was worth it.

Divided by the main railway line though Haymarket and Waverley, the north of this diverse seat includes the more affluent and Tory areas of Murrayfield, Ravelston, Orchard Brae, New Town, and Comely Bank.

The SNP is stronger in the more working class south - Gorgie, Dalry, Fountainbridge, Tollcross, Old Town, and Dumbiedykes.

Labour does well in studenty St Leonard's and northern Newington, and the Greens are strong in Broughton and Stockbridge.

Key for the two lead parties is turning out their support, especially the SNP, whose vote is softer.

Trying to defend that tiny majority is Scott Douglas, a councillor in the seat's western edge, who says unionist voters are getting behind the Tories here.

He said: "People are starting to coalesce behind the candidate who stands the best chance of defeating the SNP.

"Because we won last time, people can see that's us."

He says anger at the SNP's record and Indyref2 are factors, plus, surprisingly, Mr Robertson's big name.

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He said: "He's quite a Marmite character. He's high-profile, but that means you either like him or loathe him.

"There are some people who think he's going to be the next leader of the SNP, and that's enthused them to vote against him."

And not just unionists. Mr Douglas claims disaffected pro-Salmond nationalists plan to vote for almost anyone else.

"They see him as one of Nicola's buddies, and as Alex Salmond supporters don't want him to succeed. They won't vote for us, but might vote elsewhere."

Mr Robertson has his doubts about that. He's also sceptical of Tory claims that because they won the seat last time, they can do it again, not least because of Brexit.

A few months after Ms Davidson won Edinburgh Central, it registered one of the biggest Remain votes in the UK. Brexit is deeply unpopular here.

He said: "We shouldn't forget the Remain vote in Edinburgh Central. The Tories are running on a pro-Brexit ticket in an anti-Brexit seat. The dynamics have changed since they won the seat."

One thing Mr Douglas and Mr Robertson do agree on is the importance of the Green vote.

In 2016, Alison Johnstone, now a Green MSP, won a thumping 4,644 votes. If just 611 of those had gone to the SNP, Edinburgh Central would be a far less interesting seat today.

Mr Robertson said: "It's absolutely clear the Green vote inadvertently let the Tories in in Edinburgh Central, which I think probably horrified many people who voted Green.

"We're encouraging all non-Tories to understand it's a two-horse between the SNP and the Tories and to use their vote effectively to get the Tories out of Edinburgh Central."

Ms Johnston, who is standing again, said: "It's arrogant to suggest the SNP lost in 2016 because of Green voters. The fact is that the SNP didn't attract enough votes."