LONDON —Greater Manchester Mayor Andy Burnham is poised to challenge British Prime Minister Keir Starmer for the country’s premiership after his resounding victory in a high-stakes by-election in northern England.Burnham handily defeated his closest challenger, Robert Kenyon, the candidate for the anti-immigration Reform UK, in the seat of Makerfield, vote results showed early on Friday, securing the House of Commons seat he needs to mount a bid for the prime ministership.Thursday’s by-election was triggered with the sole purpose of providing a path to 10 Downing Street for Burnham, who is widely seen as the Labour politician best placed to unseat the embattled prime minister.Burnham secured 55% of the vote, a comfortable lead over Kenyon, who came in second place with 35%. Rebecca Shepherd of Restore Britain was a distant third, trailed by Michael Winstanley of the Conservative Party, Sarah Wakefield of the Green Party, and the Liberal Democrats’ Jake Austin.While Burnham plots his next move, the UK government now enters a new period of uncertainty, potentially facing a sixth prime minister in seven years.Starmer confirmed on Friday to the BBC that he will run in any leadership contest, indicating that any transition of power could be more volatile than Burnham might hope.Meanwhile, Burnham alluded to but did not explicitly reference his leadership ambitions in a speech on Friday.“This now is the change moment,” he said, standing in front of his supporters. “We have an opportunity to turn the tide, to make the country feel like it’s working again, to make people see that politics can make a positive difference to make people feel hope again.”Burnham, a former cabinet minister who’s been Mayor of Greater Manchester for the best part of a decade, now re-enters parliament at a pivotal moment for his party.Since winning a landslide victory in 2024 that ushered in the first Labour government in the UK in 14 years, the center-left party under Starmer has suffered a precipitous drop in popularity. This culminated in devastating losses in local council elections in early May, with Reform seeing massive gains.Growing numbers of Labour MPs called for Starmer to quit, but Burnham unable to run as party leader – and hence prime minister – since rules and convention state that only serving MPs can do so.On May 14, Labour MP for Makerfield Josh Simons announced he would be stepping aside “so that Andy Burnham can return to his home, fight to re-enter Parliament, and if elected, drive the change our country is crying out for.” Labour’s powerful National Executive Committee, which blocked a previous attempt by Burnham to run for parliament, cleared him to stand.Reform leader Nigel Farage said it was a “disappointing morning” as the by-election was “a dramatic, emphatic win for Andy Burnham.”Burnham faced a delicate and arduous campaign in what quickly emerged as a two-party race – but not against the Conservative Party, the official opposition in parliament. Instead, his main challenger was Kenyon, a 41-year-old plumber, who was focused on tapping into the economic grievances, and immigration concerns, of the overwhelmingly White population of Makerfield, while repeatedly accusing Burnham of using the constituency as a “stepping stone.”In his victory speech, Burnham said Makerfield “will never be a stepping stone to me, but instead will be my touchstone” that would stand as a “test at the heart of British politics” to “ensure that the places Westminster has neglected will now get fairness.”