Labour Loses Caerphilly By-Election for the First Time in 100 Years

Image Credit: Senedd Cymru via Wikimedia

Following a windy polling day, Labour lost one of its heartland seats in Caerphilly, which had a Labour MS since devolution in 1999. Welsh Labour could be considered one of the most successful democratic political parties in history, based on continued electoral success. They have won a plurality of Welsh seats, both in Westminster and later in the Senedd, since 1922. Yet following declining national polling since Labour’s landslide victory at the 2024 general election, with Labour’s approval rating falling to 20% in a recent poll, Welsh Labour has also become increasingly unpopular. This is especially notable following the 2021 Senedd election, where Mark Drakeford led the party at the height of his popularity. 

The by-election took place following the death of Hefin David MS, and was a crucial test for the three major parties in Wales (Labour, Reform and Plaid Cymru) in the lead-up to the Senedd elections in May 2026. All three parties framed the election as a two-horse race, yet always between different parties. Reform led the polling by a margin of 4% in the run-up to the by-election.

Campaign offices from all three of the major parties contesting the seat dotted Caerphilly's High Street. While the Reform and Plaid Cymru offices were covered in party branding, Labour's office was far less recognisable. Speaking to last-minute canvassers for both Labour and Plaid Cymru (Reform did not canvass on polling day), the general consensus was that the number of lifelong Labour voters who would switch to voting Plaid was going to be significant.

When the results finally came in in the early hours of the 24th of October, the reality defied the polls; a record turnout of just over 50% led to Plaid Cymru and their candidate Lindsay Whittle winning 47.4% of the vote.