Key topics:Labour collapses in Caerphilly, Plaid Cymru wins with 47% vote.Tactical voting blocks Farage, boosts turnout over 50%.UK politics fragments; Labour must adapt to multi-party reality..Sign up for your early morning brew of the BizNews Insider to keep you up to speed with the content that matters. The newsletter will land in your inbox at 5:30am weekdays. Register here.Support South Africa’s bastion of independent journalism, offering balanced insights on investments, business, and the political economy, by joining BizNews Premium. Register here.If you prefer WhatsApp for updates, sign up to the BizNews channel here..By Rosa Prince.Welsh Labour has long been the most successful political party in the democratic world — until now. Its unbroken run in general and, since the Welsh Assembly’s formation in 1999, regional elections stretches back more than 100 years. But the results of a bellwether by-election in South Wales suggests that domination is at an end.It was a grim night in the valleys for the UK’s ruling party, whose plunging popularity is improving the chances of the hard-right populist Nigel Farage becoming prime minister. But the electoral math does offer some shred of comfort for those who dread that fate.First things first. Labour’s vote collapsed in the Caerphilly count, which was triggered by the death of Welsh Assembly (or Senedd) member Hefin David. The nationalist Plaid Cymru triumphed with 47% of the vote, defeating Farage’s Reform UK on 36%, and driving Labour into third place with just 11% of the vote. That’s a humiliating fall of nearly 25 points from the last time the constituency was contested in 2021.With full Senedd elections coming in the spring, Caerphilly backs up polling that shows Labour’s unbroken run is doomed. It may end up with no role in the Welsh government other than, maybe, as a junior partner to Plaid..Read more:.Farage's Reform Party, not the Tories, is Starmer’s real opposition: Adrian Wooldridge.Yet there are silver linings amid the gloom — along with the painful lessons. Beleaguered Prime Minister Keir Starmer will feel a smidgen of relief at being defeated by friend not foe. And that’s not just because his party is used to working in the Senedd with Plaid, which offers a less punchy version of patriotic politics than the Scottish Nationalist Party.Reform fancied its chances in Caerphilly, with Farage visiting the town several times. A victory party complete with balloons was hastily cancelled, according to one report. Given Reform didn’t exist four years ago, it’s still a strong result. But it arrests the narrative of Farage the unstoppable insurgent, and begs the question of whether his support has reached a ceiling. When voters want to punish the establishment parties, they have other choices.Turnout was key to blocking Farage. At more than 50% it was a record in a Welsh by-election. Polls showing Reform ahead in the days running up to the vote were a spur. Younger voters and commuters who work in the Welsh capital Cardiff played a part. Reform’s older, more inward-looking supporters were less motivated.Tactical voting appears to have created a winning anti-Farage coalition. Plaid said Labour voters and even party members told canvassers they’d be backing the nationalists to keep Reform out.As well as depressing’s Labour share, tactical voting brutalized the Conservatives. A call from former minister Jacob Rees-Mogg to back Farage didn’t deliver victory and was disastrous for the Tories, who flatlined at 2%. Astonishingly, Westminster’s two main parties, who’ve traded power for a century, won less than 15% between them. That’s a lesson for both Starmer and Conservative leader Kemi Badenoch about pandering to Reform voters.Badenoch must be wary now about tactical voting if her party is to avoid oblivion. For Starmer the emergence of five-party politics means he must be as alive to the threat on his left as that to his right. And he must be clever about non-aggression pacts to tap the “anyone but Farage” sentiment.In Wales, Labour suffered a double incumbency impact. Voters were irritated by the administration’s tin ear in introducing a 25 mile-per-hour speed limit on empty rural roads, as well as the poor performance of the (devolved) National Health Service and a donations scandal. Labour’s Welsh First Minister Eluned Morgan’s attempts to distance herself from Starmer couldn’t remedy the anger about policies such as stopping families claiming benefits for more than two children. The cost of living crisis was a clincher, as were attempts to cut winter fuel payments for pensioners.Outside Wales, Scotland and Northern Ireland, the threat to Labour isn’t nationalist but the booming Greens. As Sam Freedman has written, fragmenting politics on the left and right means elections are being won and lost on much narrower margins. The days of giant majorities, as in Wales where Labour activists used to joke they needed to weigh rather than count votes, are over.The lesson is the same across the UK. In 2024, 85% of parliamentary seats were won on less than half the vote. It was 35% in 2019. Labour secured a landslide but with the lowest ever vote share for a winning party: 34%.Five UK-wide parties are polling within 11 points of each other, while nationalists in Scotland and now Wales are surging. Dozens if not hundreds of seats at the next election could have four or five parties with a chance of winning. Shifting a few votes here or there will mean the difference between defeat and victory. Tactical voting will become the norm; if only the parties make clear which way the tactics lead.To win power again in Wales in 2026 and the UK in a general election that must come by 2029, Labour has to hope that Caerphilly does indeed show the limit of Reform’s appeal. It must then persuade that majority who don’t want Farage in Downing Street that it is the best means of keeping him out. That won’t be easy with Starmer’s weak communication. It’ll need to canny, too, about tactical voting as it’s been before..Read more:.Nigel Farage in the US likens UK’s online free speech censorship to North Korea.Of course, the best route will be defusing the cost of living bombshell and other policies driving Labour voters away. Trying to steal Farage’s thunder, as Starmer did with his regrettable “island of strangers” speech in May, won’t cut it. If he can’t stop leaking supporters to the Greens, Liberal Democrats and nationalists, he’ll at least need to work with them.As he triumphed in Caerphilly at the 14th time of asking, Plaid’s Lindsay Whittle had a message for Labour: “You better go back to the drawing board,” he said. “Think again because you’re on the way out.” If Labour doesn’t listen, he’ll be proved right..© 2025 Bloomberg L.P.