Plaid Cymru’s extraordinary by-election victory in Caerphilly has sent shockwaves through Welsh and UK politics, delivering a humbling blow to Labour’s dominance and Westminster’s big beasts. This result marks a pivotal turning point, with implications far beyond the Welsh Senedd and into the corridors of national power. By turning the Labour heartland into a stage for Plaid Cymru’s resurgence, the 2025 Caerphilly by-election represents a seismic shift in the country’s political landscape.
The By-Election: Record Turnout & a Historic Upset
On October 23, 2025, Caerphilly, a Labour-held constituency since 1918, witnessed a political earthquake. For the first time, Plaid Cymru’s Lindsay Whittle claimed victory in the Welsh Parliament seat, ending Labour’s stranglehold in a contest that drew a record turnout of over 50%, the highest ever for a Senedd by-election. Plaid Cymru secured nearly 47% of the vote, delivering a swing of almost 27% from Labour and outperforming Nigel Farage’s surging Reform UK, which placed a strong second.
Labour’s collapse was stark and unprecedented. Richard Tunnicliffe, Labour’s candidate, limped into third place with just 11% of the vote, far below expectations, and a disastrous drop from the 47% Labour achieved in 2021. The Tories managed only 2%, further underlining how the seismic battle was now between Plaid and Reform.
Plaid Cymru’s Message: Hope, Change, and National Vision
For Plaid Cymru, the win was more than electoral arithmetic; it was an emphatic endorsement of the party’s positive, pro-Wales vision. Leader Rhun ap Iorwerth declared, “The people of Caerphilly have spoken loud and clear. They’ve chosen hope over division, and progress over the tired status quo”.
Lindsay Whittle, the victorious candidate, known locally as “Mr Caerphilly,” fought his 14th parliamentary contest at age 72 and finally delivered victory, dedicating his win to the late Labour Member Hefin David. Whittle’s decades-long commitment to Plaid and to local causes lent a human dimension to Plaid’s triumph, symbolising the emergence of local champions over party machines and slogans.
Plaid’s messaging was clear: they are now the “real choice” for Wales, the only party able to deliver meaningful change and resist the rise of billionaire-backed alternatives like Reform UK. The victory, according to Whittle, shows what’s possible when communities unite behind practical solutions and priorities that matter most to them.
Reform UK: Second Place but “Decimating Labour”
Reform UK, led by Nigel Farage, surged to a forceful second place, capturing over a third of the vote (35.9%). This performance was a dramatic jump from their previous results and demonstrated the party’s newfound resonance, though still not enough to top Plaid Cymru’s grassroots campaign. Reform’s Llyr Powell focused his concession on the “massive gain” against Labour, vowing improved strategies for the 2026 Senedd elections.
Labour’s Collapse: After a Century of Dominance
Labour’s defeat is described in every major account as humiliating and historic. The party, which has led Wales for over a hundred years and run the devolved administration since 1999, finished a distant third. Beyond the constituency, this result throws Labour’s grip on power in Cardiff Bay into question, coming just ahead of the crucial budget vote in January.
With Labour now two seats short of a majority in the Senedd, there are fears the government will struggle to see major legislation, especially critical budget proposals, through the Welsh Parliament. Party leader Eluned Morgan acknowledged the need for lessons, vowing to listen and return stronger, but the result starkly demonstrates Labour’s weakening connection with its traditional base.
Westminster’s Reckoning: Big Beasts Humbled
The Caerphilly result is more than just a local upset; it is a direct rebuke to the so-called “Westminster big beasts.” Only 13% of the electorate backed Labour and Conservative parties combined, underlining a massive disconnect between national party leadership and the Welsh electorate’s shifting mood.
The outcome is deeply troubling for Prime Minister Keir Starmer, who now faces renewed scrutiny of his leadership and party strategy across the UK. For Farage’s Reform, failure to claim first place stings, but their second-place surge suggests the party is increasingly capable of challenging both Labour and Plaid in key Welsh and UK seats in future polls.
What Next for Wales?
Plaid Cymru’s resounding triumph suggests an electorate hungry for change. The party’s local focus, positive vision, and persistent campaigning have paid off, inspiring both veteran supporters and a new generation of voters seeking Welsh solutions to Welsh challenges. For Plaid, this is both a crowning achievement and a call to action ahead of the 2026 Senedd elections.
For Reform and Labour, Caerphilly is now a critical lesson in the perils of complacency, the volatility of the modern electorate, and the importance of grassroots campaigning. The loss closes a century-old chapter in Welsh Labour history while opening a new era of unpredictability—and opportunity—in Welsh and UK politics.
