MOST landmark “change” elections feature a major symbolic scalp. For Labour in 1997, it was their defeat of Michael Portillo in Enfield Southgate. For the SNP in 2019, it was the astonishing achievement of ousting the Liberal Democrat leader Jo Swinson in East Dunbartonshire.

This year, if Labour do make a telling comeback in Scotland, they’ll be looking to dislodge a big name SNP MP as the icing on the cake. A prime target is the SNP Westminster leader Stephen Flynn in Aberdeen South, which unfortunately is indeed a potentially vulnerable seat.

However, Flynn possesses a secret weapon that has an excellent chance of saving his bacon on July 4. That weapon is Unionist voter confusion.

If a voter’s priority is to topple Flynn, it may be unclear to them which Unionist party offers the best opportunity of doing that.

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Aberdeen South contains some of the most affluent localities in Scotland, and is therefore a far cry from being the archetypal sort of Scottish constituency in which the Labour vote was weighed rather than counted for decades until the SNP suddenly broke through in 2015.

In fact, the seat changed hands between the two major Unionist parties on no fewer than five occasions between the 1960s and the 1990s, and if anything it tended to lean more towards the Conservatives. Typically Labour only won there when they were in landslide territory in the UK, or in Scotland, or in both. It was one of those episodes that gave the future first minister Donald Dewar the opportunity to cut his teeth as a parliamentarian when he was elected Labour MP for Aberdeen South in Harold Wilson’s landslide of 1966.

But Dewar unsurprisingly lost the seat when the Conservatives returned to power in 1970, and what is perhaps more telling is that the Tories retained it in the two General Elections of 1974, both of which were narrowly won UK-wide by Labour.

Two decades later, it was also notably the only seat anywhere in Britain gained by the Tories directly from Labour during John Major’s slender 1992 election triumph.

So the Tories have a reasonably compelling story to tell budding tactical voters in Aberdeen South. They can say that it’s historically a Conservative-leaning seat, that Ross Thomson of the Tories was the most recent non-SNP MP there, and that the Tories remained clearly the main local challengers to the SNP in the 2019 election, taking more than three times as many votes as third-placed Labour.

But Labour have an equally persuasive counter-argument. They can point out that the Tory slump in the Scotland-wide polls makes it almost inconceivable that the Conservative vote in Aberdeen South will actually increase this time.

They can argue that although they need a much bigger swing from the SNP than the Tories would require, that is nevertheless the only plausible way in which Flynn will be defeated.

Voters are therefore likely to be bamboozled by contradictory leaflets featuring bar charts purporting to prove that “only the Conservatives can stop the SNP in Aberdeen South!” and “only Labour can stop the SNP in Aberdeen South!”

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Doubtless the Liberal Democrats will join in too. Their own case for being the main Unionist challenger is less convincing but they can never resist a good bar chart, and they’ll be able to point to their former Scottish leader Nicol Stephen’s 12-year spell as MSP for the equivalent constituency in Holyrood.

Clearly the most stress-free way for Stephen Flynn to defy the Unionist challenge would be for the SNP to recover strongly in the polls before election day. But even if that doesn’t happen, it’s genuinely possible that the Unionist parties will cancel each other out in Aberdeen South, and that the Unionist vote will be split in such a way that Flynn is able to hold on with reduced support.