Labour party veteran and Greater Manchester mayor Andy Burnham is looking to win the parliamentary by-election for the Makerfield constituency in northwestern England, so that he can then try to replace Starmer as prime minister.Polling stations opened at 7:00 am (0600 GMT). They will close at 10:00 pm, with counting due to begin straight away.Pollsters expect Burnham to win the historic contest, but he faces a tough fight from the hard-right Reform UK party."Almost undoubtedly it's in the hands of the voters of Makerfield as to whether or not Burnham becomes prime minister," political scientist John Curtice."If Burnham does win, his path to 10 Downing Street looks to be relatively assured. If they deny him the opportunity, it may be that Starmer will survive, at least for the time being," he told AFP.Starmer, in power since July 2024, has been clinging to power by his fingernails since Labour suffered a drubbing in local and regional elections last month.He has been rocked by several policy U-turns and a scandal over his appointment of ex-Jeffrey Epstein associate Peter Mandelson as the UK's ambassador to Washington.The 63-year-old prime minister has endured several ministerial resignations and rock-bottom personal poll ratings, with Reform leading national surveys for over a year.But Starmer, an ex-lawyer who has refused to quit, insists his landslide election victory over the Conservatives 21 months ago gives him a five-year mandate to govern.'King of the North'Impatience within the centre-left Labour party ramped up in May when Labour MP Josh Simons announced he would stand down so Burnham could try to return to parliament and run for leader.While Makerfield's 76,000 electorate typically votes Labour, Simons won a majority of only around 5,300 at the 2024 general election.Reform, led by anti-immigrant firebrand Nigel Farage, also won every council ward in the predominantly white, working-class area during last month's council polls.But the personal popularity of Burnham -- a three-term mayor of Greater Manchester nicknamed the "King of the North" -- is likely to see him triumph over Reform candidate Robert Kenyon, polls predict.Local plumber Kenyon has also been dogged by offensive remarks he previously made about women, while the fringe Restore Britain party is expected to split the hard-right vote.In Ashton-in-Makerfield, 61-year-old Hazel Ellis told AFP she planned to vote for Reform."I'm willing to give them a go because this is the last hope for Britain now," she said.Coronation?In nearby Bryn, twenty-three-year-old Finn Knowles told AFP Burnham was "a better option" than Starmer."He doesn't really know what he wants to do," the pub worker said of the prime minister.Burnham, who polls show is Labour's most popular politician, hails from the party's so-called soft-left wing and has been an outspoken critic of Starmer's more-centrist rule.