The National:

EDINBURGH CENTRAL

Winner in 2016: Ruth Davidson (Conservative)

RUTH Davidson’s narrow victory over the SNP in Edinburgh Central five years ago, which made her the Holyrood Parliament’s own local MSP, was a massive upset.

It was a double blow for the SNP, because it provided the symbolic icing on the cake of the Tory surge, and it was also a lost seat in very real terms – there was no SNP seat on the Lothian list to compensate for it.

If the SNP candidate, Alison Dickie, had held the constituency as expected, there would have been 64 SNP seats in the Parliament, which would have tied the SNP government with the combined forces of the opposition once the presiding officer was excluded from the calculation.

Davidson’s win in the constituency was therefore enough in itself to tip the balance and leave the SNP in minority territory.

The National:

There’s no mystery about why or how the surprise result happened. Unlike all four previous elections in the constituency, the Greens decided to intervene by putting up a candidate, and they selected their incumbent Lothian list MSP Alison Johnstone.

She finished fourth, with a highly significant 14% of the vote. Although local election transfers over the years have demonstrated that the SNP are by no means the second choice of all Green supporters, it’s inevitably the case that far more Greens will vote SNP in the absence of a Green candidate than will vote Tory.

That helps explain why the SNP vote fell by 4% in Edinburgh Central, compared to a 1% increase in the party’s national vote share.

Even if the SNP had merely retained the 33% of the vote that their former MSP Marco Biagi took in 2011, that would have been enough to hold off Davidson’s challenge.

The conclusion is inescapable: the Green intervention was, in all likelihood, indirectly responsible for the Tory gain.

In fairness to the Greens, though, they could reasonably claim that Davidson’s outright victory was largely unforeseeable.

When Biagi had gained the seat, it was from former Labour cabinet minister Sarah Boyack, not the Tories. Boyack had been the incumbent for 12 years, and the Tories had never finished higher than fourth place.

It required an enormous 15% increase in the Tory vote – well in excess of the party’s national performance – for Davidson to jump from fourth to first.

But now that we’ve had the practical demonstration that Edinburgh Central is winnable for the Tories, many independence supporters are puzzled that the Greens have once again put up Johnstone (below) as a candidate in the constituency.

The National: Alison Johnstone MSP.

The Greens quite reasonably point out that there are many important issues other than independence and that they are providing a distinctive alternative to both the Tories and the SNP – although the counter-argument would be that putting the pro-independence majority at risk on the constituency ballot is not easily reconcilable with the Greens’ claims to be the safest option for maximising pro-indy representation on the list ballot.

A further obstacle facing the SNP in their quest to recapture the seat is the social media buzz surrounding the independent candidacy of Bonnie Prince Bob, who believes the SNP are a “bourgeois neoliberal” party of “careerist impostors”.

As with the Greens, it’s reasonably safe to assume that if he takes votes, more will come from the SNP than from the Tories. Simply to become the SNP candidate this year, the party’s former depute leader Angus Robertson had to win one of the most epic and controversial internal selection battles in Scottish Parliament history.

Joanna Cherry only withdrew from contention after being deterred by a rule change that many people suspected had specifically targeted her. Biagi launched a bid to reclaim his old seat, with surprise help from “Patronising No Lady” of Better Together fame.

Having navigated his way through all that, it would be bitterly ironic if Robertson ended up losing to the Tories anyway.

His strongest card may be to remind voters that, while the involvement of other candidates could throw the Tories a lifeline, it’s not actually compulsory for independence supporters to walk into the trap.

Whatever the outcome, though, we at least have the consolation of knowing that Davidson has asked her final question at FMQs.

She’s off to a much higher place where she no longer needs to trouble herself with anything so vulgar as election campaigns.