In the wake of Plaid Cymru’s victory in Caerphilly and Reform UK’s reshaping of the political landscape, Scotland’s unionists need to rethink whether tactical voting can still contain the SNP, writes Herald columnist Mark McGeoghegan.

Labour’s defeat in last week’s Welsh Senedd by-election in Caerphilly came as no surprise to anyone who had been paying attention to the contest, but it was still crushing. They came a distant third behind Plaid Cymru and Reform UK in a seat they had held comfortably since the Senedd was established in 1999, and a part of Wales where Labour have won every general election since 1918.

What was somewhat surprising was the scale of Plaid’s victory, beating Reform by 47% of the vote to 36%. A poll of the constituency had previously suggested that Reform would win, and they were bullish going into the count on Thursday night. In the end, an anti-Reform voted coalesced not around the Labour incumbents, but Plaid, delivering them victory.

Caerphilly marked the emergence of a relatively new phenomenon in British politics. We’re used to tactical voting against parties like Reform, but not those tactical votes shifting in such a dramatic manner to a party with no history of success in a constituency.

Plaid presented the by-election as “a clear choice for Caerphilly” between them and Reform, between left and right, and between two nationalisms, Welsh and (essentially) English. They dispatched Labour........

© Herald Scotland