IT’S a mystery that might have left even Sherlock Holmes stumped: who or what made the Liberal Democrats vanish in a puff of smoke in Gordon?

From the constituency’s creation in 1983, it had been held for decades by Malcolm Bruce – at one time the leader of the Scottish LibDems – and even in the post-indyref election of 2015 when the SNP swept almost every constituency in Scotland, the local LibDem vote remained at a very strong 33%, easily enough for second place.

But then out of nowhere at the 2017 general election, the LibDems collapsed to just 12%. The lost votes seemed to transfer wholesale to the Conservatives, whose support soared by an almost ludicrous 29 points, allowing them to jump from a distant third into first place, defeating the SNP’s incumbent MP Alex Salmond, who had previously represented the equivalent constituency in the Scottish Parliament.

The result was so peculiar it even caught out the normally very reliable BBC exit poll, which predicted that the SNP had lost in Gordon to the Lib Dems rather than to the Tories.

It had reached that conclusion by extrapolating from the trends in other seats like Edinburgh West and East Dunbartonshire where the Lib Dems were starting from a clear second place and were significantly strengthening their support with help from Unionist tactical voters.

For Gordon to have gone in such a radically different direction can only mean that the Lib Dems more or less left the field clear for the Tories.

A cynic might wonder if there was an informal understanding between the Unionist parties to split Scotland into “spheres of influence”, giving one party in each area a free run at targeting the anti-SNP tactical vote.

At the very least, the Lib Dems had clearly decided to abandon Gordon and concentrate their resources elsewhere. And that decision has very concrete consequences for the contest in the newly redrawn Gordon and Buchan constituency at this year’s General Election.

In a parallel universe where the LibDems hadn’t thrown in the towel seven years ago, they would currently be in a straight fight with the SNP. That would be an unequal battle in the LibDems’ favour because their national vote is holding up and they generally find it very easy to pitch for anti-SNP tactical votes in areas where they can win.

READ MORE: This constituency will be a tough result to call following boundary changes

Instead, the SNP’s only realistic opponents locally are the Tories, which in current circumstances ought to be a considerably easier proposition.

The disdain for Rishi Sunak’s administration is so great at present that it’s unlikely many LibDem and Labour supporters will be queuing up to vote tactically for the Tories to keep the SNP out.

But it still won’t be straightforward for the SNP. Although the old Gordon seat was one of the majority of Scottish Tory-held constituencies that the SNP gained back at the 2019 General Election, the margin of victory was a wafer-thin 1.4%, and the recent radical boundary changes means the new version of the seat reverts to having a notional Tory majority of more than five percentage points.

The new voters that have entered into the mix were previously within the old Banff and Buchan constituency, which voted to leave the European Union in numbers not matched anywhere else in Scotland. That may be an advantage for the Tories, especially as even in the old Gordon seat the Leave vote was a relatively high 44%.

The Buchan factor is a double-edged sword, though, because those new voters were until a few weeks ago represented by popular Tory MP David Duguid (pictured).

They may well be disgusted by the fact that the Scottish Conservative leader Douglas Ross seemed to exploit Duguid’s recent illness as a pretext to install himself as candidate in the neighbouring new constituency of Aberdeenshire North and Moray East, where it had been widely expected Duguid would be defending his seat.

Voters in Gordon and Buchan are not directly affected by that episode but they may still be reluctant to reward such cynical behaviour, and some usually reliable Tory voters might be looking for an alternative on this one occasion.

In a close race, that could just be the decisive element that helps get the SNP’s incumbent MP Richard Thomson over the line.