In a result that’s sent shockwaves through the Welsh political landscape, Plaid Cymru has seized victory in the Caerphilly Senedd by-election, marking what party leader Rhun ap Iorwerth called “a reset for Welsh politics.” The by-election, held on October 23, 2025, saw Plaid’s Lindsay Whittle triumph with 47% of the vote amid a record 50% turnout—an outcome that has upended expectations in a seat long considered a Labour stronghold.
The drama of the night was palpable. Reform UK, led by the ever-controversial Nigel Farage, came in second with 36%, while Labour, the party that once commanded the valleys, was relegated to a distant third with just 11%. The Conservative Party, meanwhile, barely registered, scraping together a mere 2% of the vote. Together, the two traditional Westminster giants managed only 13%—a statistic that would have been unthinkable just a decade ago.
BBC political editor Chris Mason summed it up succinctly: Labour was “humbled, pummelled, crushed,” and the Tories “managed just 13% of the vote between them. Yes, you read that right.” According to The Guardian, the result is a clear sign that “UK politics is moving at speed, with voter loyalties shifting and atomising in unprecedented ways. Those who cannot adapt will be crushed.”
Plaid Cymru’s Lindsay Whittle, a veteran councillor in the Penyrheol ward and leader of the group on Caerphilly Council, secured the seat with a swing of nearly 27% from Labour. Speaking after his win, Whittle didn’t mince words: “The Labour Party now is dead. And I think it’s time for a new Wales, under new leadership, with new vision, new ideas. And that’s exactly what we’re offering with our leader Rhun ap Iorwerth who will make an excellent first minister next May. And first minister, he will be.”
Rhun ap Iorwerth echoed the sentiment, describing the victory as “real evidence” that people are putting their “faith” in Plaid Cymru. He added, “This is a reset for Welsh politics.” The party’s triumph marks the first time in more than a century that Labour has lost a vote in this former mining town, a fact not lost on political analysts or the candidates themselves.
For Labour, the night was nothing short of a disaster. The campaign was marred by internal strife, with a council leader quitting over lack of support for both Keir Starmer and by-election candidate Richard Tunnicliffe. Welsh First Minister Eluned Morgan admitted, “This was a bad result for Labour,” but insisted she would not resign, stating, “I’ve got too much work to do.” She also revealed she had spoken to Starmer, who “realises responsibility to help out in Wales.” Morgan acknowledged, “There are serious lessons for us to learn here at all levels of government.”
Polling expert John Curtice, writing in The Times, warned that Labour is “in severe trouble” in Wales after the humiliating defeat. He observed, “The party is losing ground to its left as well as its right. In Caerphilly it was Plaid who were able to do most of the damage.” The result, Curtice argued, reinforces the narrative that Labour faces a double threat, and not just from the right-wing insurgency of Reform UK.
Reform UK, for its part, had high hopes. The party’s chairman, David Bull, told BBC Breakfast that their “meteoric rise” in just four years was extraordinary, even if they fell short of victory. “I haven’t seen anything like this—the fact we have this stratospheric rise is extraordinary,” Bull said. He insisted the result shows “two-party politics is dead,” noting that Labour had been “trounced” and the Conservatives “virtually wiped off the electoral map.” Bull did express disappointment at not winning, suggesting tactical voting may have played a role.
Nigel Farage, who visited Caerphilly three times during the campaign but was conspicuously absent when the results were declared at 2:10 a.m., took to social media to frame the contest ahead: “The Senedd elections next year are a two-horse race between Reform UK and Plaid Cymru.” Farage blamed the “total collapse” of the Labour vote to Plaid for Reform’s inability to clinch the seat.
Reform’s regional hurdles were apparent. While 36% is a “solid performance for an upstart,” as Mason noted, “insurgencies remain insurgent by winning—and they were easily beaten.” There’s a sense that, at least in Wales, Reform struggles to become the default ‘none of the above’ option when another party—Plaid Cymru—lays claim to that mantle as well. Llyr Powell, Reform’s candidate, remained upbeat, expressing confidence that his party would win enough seats in the Senedd election next May. A Reform UK Wales spokesman declared, “The Labour Party is finished in Wales, and the Conservative Party has gone the way of the dodo. This is a historic realignment in Welsh politics.”
The Conservative Party’s dismal showing—just 2%—left unionists reeling. Andrew RT Davies, former Welsh Tory leader, called the result “a wake up call for unionists,” warning, “Separatism is corrosive, with the aim breaking apart our nation and no regard to its consequences on the living standards of the people of Wales.” Davies argued that Plaid Cymru’s victory should prompt unionists to “show the people of Wales the real Plaid.”
For Labour, the defeat in Caerphilly is more than just a local embarrassment. It’s a warning shot ahead of the full Senedd elections scheduled for May 2026. As Wales Online put it, the by-election “drubbing” could reinforce concerns about Labour’s prospects next spring, with canvassers now questioning whether it’s worth their effort to go door-knocking over the winter.
Adding to Labour’s woes are accusations of national unpopularity and policy missteps. Former Labour MP for Caerphilly, Ron Davies—now with Plaid Cymru—called the result “devastating” for Starmer’s party, citing financial decisions such as means testing the winter fuel payment as reasons for Labour’s decline.
Downing Street, meanwhile, attempted to put a brave face on the result. The Prime Minister’s press secretary acknowledged, “By-elections are always difficult for incumbent governments. This one is no different, but we are determined to show the people of Caerphilly and working people across Wales the change the UK Government is delivering hand in hand with the Labour government in Wales.”
As the dust settles, one thing is clear: the Caerphilly by-election has rewritten the rules of Welsh politics. With Plaid Cymru ascendant, Reform UK surging, and Labour on the ropes, all eyes now turn to the Senedd elections in May 2026. The old certainties are gone, and the campaign season has only just begun.
