The political landscape of Wales was shaken to its core this week as Plaid Cymru scored a historic victory in the Caerphilly Senedd by-election, ending more than a century of uninterrupted Labour dominance in the constituency. The result, declared late on October 23, 2025, marked the first time since 1918 that Labour failed to capture the seat—an outcome that sent shockwaves through both Welsh and UK politics.
Plaid Cymru’s candidate, Lindsay Whittle, a 72-year-old political veteran who had stood unsuccessfully in the area 13 times since 1983, finally claimed the prize with 15,960 votes. His triumph was not only personal but also deeply symbolic for his party and for Wales. Overcome with emotion as the result was announced, Whittle told supporters, “Listen now Cardiff and listen Westminster—this is Caerphilly and Wales telling you we want a better deal for every corner of Wales. The big parties need to sit up and take notice.” According to Sky News, he added, “Wales, we are at the dawn of new leadership, we are at the dawn of a new beginning—and I look forward to playing my part for a new Wales, and in particular, for the people of the Caerphilly constituency.”
The by-election was triggered by the death of Hefin David, the sitting Labour Member of the Senedd. Historically, Caerphilly has been considered the beating heart of Welsh Labour, with its parliamentary roots in the party dating back to Alfred Onions’ victory in 1918. The seat has been a Labour stronghold at both Westminster and the Senedd since the creation of the devolved assembly in 1999, making this defeat all the more significant.
The contest was widely seen as a two-horse race between Plaid Cymru and Reform UK, the right-wing insurgent party led by Nigel Farage. Reform UK’s candidate, Llŷr Powell, was the bookmakers’ favourite but ultimately finished second with 12,113 votes—a staggering improvement from the party’s meager 495 votes in 2021. Labour’s Richard Tunnicliffe suffered a crushing blow, coming in third with just 3,713 votes. The turnout was 50.43%, a notable increase from the 44% seen in 2021 and the first time a Senedd election in Wales has ever surpassed the 50% threshold, as reported by BBC News.
For Labour, the loss was a bitter pill to swallow. Prime Minister Sir Keir Starmer expressed his dismay, saying, “I’m deeply disappointed in the results. I’m not going to suggest otherwise. We clearly need to do much more.” Welsh Labour described the contest as a “by-election in the toughest of circumstances, and in the midst of difficult headwinds nationally.” Labour’s deputy first minister in the Senedd, Huw Irranca-Davies, urged the party to refocus on “bread and butter things: cost of living, the state of the local community, the high street, the green spaces, the money in people’s pockets.” First Minister Eluned Morgan also acknowledged the party’s failings, stating, “We take our share of the responsibility for this result. We are listening, we are learning the lessons, and we will come back stronger.”
Plaid Cymru leader Rhun ap Iorwerth was quick to seize the momentum, declaring the result “the start of a reset of politics in Wales.” He told Sky News, “I want to see that through now. I’ve made it clear, said it in my conference speech a couple of weeks ago, we have to replace Labour. And it’s not just for its own sake, it’s so we get better outcomes for Wales. That’s what Plaid Cymru’s always about.” Ap Iorwerth also emphasized that the victory demonstrated Plaid’s ability to “win in any part of Wales,” while cautioning that the party would take nothing for granted ahead of the Senedd elections in May 2026.
The by-election’s outcome reflected not just local dynamics but a broader shift in Welsh political sentiment. As The Conversation noted, the result “shows a mass abandonment of the Labour party, providing behavioural proof of a wider pattern of Welsh Labour abandonment captured in national polling.” The willingness of former Labour voters to support Reform UK on the right and Plaid Cymru on the left highlights Labour’s challenge in appealing to a divided base. Some voters, frustrated by the perceived lack of progress on key issues under Starmer’s leadership, opted for Reform, while others coalesced around Plaid as the best bulwark against the rising right-wing tide.
Reform UK’s impressive showing—leaping from 2% of the vote in 2021 to over 36% this year—positions it as the de facto right-wing alternative in Wales. Party chair David Bull attributed the loss to tactical voting, suggesting that a recent poll showing Reform in the lead may have prompted Liberal Democrat and Conservative supporters to back Plaid Cymru to keep Reform out. Nigel Farage, meanwhile, argued that the result set up a “two-horse race between Reform UK and Plaid Cymru” for the 2026 Senedd elections.
Labour’s defeat in Caerphilly has immediate implications for its ability to govern in Wales. The party is now two seats short of a majority in the Senedd, complicating its efforts to pass crucial budget measures on the NHS, education, and other services. Talks with opposition leaders have already begun as Labour seeks a path forward.
For Plaid Cymru, the victory is a significant boost as the party celebrates its centenary. While independence for Wales remains a long-term goal, ap Iorwerth has downplayed it as a first-term priority, focusing instead on practical solutions and “a positive, pro-Wales vision.” Lindsay Whittle, who previously served in the Senedd from 2011 to 2016 and has been a fixture in Caerphilly local politics for nearly five decades, pledged to “work like a Trojan for every man, woman and child.” He paid tribute to the late Hefin David, saying his “kindness” was the “guiding spirit” of the campaign.
The by-election also highlighted the fluidity of Welsh politics in the current climate. Tactical voting, protest sentiments, and shifting party loyalties all played a role in the outcome. With the removal of the single-seat tier in future Senedd elections, the incentives for tactical voting may be diminished, potentially altering the political calculus in May 2026.
Whatever the future holds, one thing is certain: Caerphilly’s by-election has rewritten the rules of Welsh politics. As Whittle put it, “I believe the world is watching Wales, an emerging nation starting to control our lives again.” The next chapter will reveal whether this is a fleeting anomaly or the dawn of a new era for Wales.
