As British Prime Minister Keir Starmer flies back from the G7 leaders’ summit in Evian on Wednesday, he may well reflect on the impending loss of the privileged trappings of a national leader. His time left in office could be measured in days if his popular challenger Andy Burnham wins Makerfield in the most consequential by-election in recent political history. The early hours of Friday are likely to reveal the Manchester mayor as triumphant, seen as the Labour leader to head off Nigel Farage’s populist right-wing Reform party, and could very soon be installed in Downing Street. But Mr Starmer continued his rearguard fight on Wednesday. He declared that Mr Burnham could “play a big part” in government, signalling that he would invite him to join the cabinet. “Andy is a great asset and, yes, I want him to have a big role in government,” the Prime Minister told reporters in France. Asked if he would call Mr Burnham at the weekend and invite him to join the cabinet if he wins in Makerfield, Mr Starmer said: “Well, I’m sure I’ll talk to Andy after the weekend.”Manchester Mayor Andy Burnham in Ashton-in-Makerfield. AFPInfoHowever, there is a growing consensus that Mr Starmer will have only the weekend to consider whether to resign and allow a “coronation” for Mr Burnham or to fight on and face a potential cabinet revolt. His position in Evian was the latter. “I don’t think there should be a challenge,” he said. Referring to previous Conservative leadership battles, he added: “I think history, particularly the last government, shows that that isn’t a successful way for a government to behave. But if there is a challenge, then I intend to fight.”While his fighting talk is to be expected, much will depend on the size of Mr Burnham’s win in Makerfield. His credentials will be undermined if he just scrapes through. Polling shows that his margin of victory could be between 5 and 12 per cent over Reform’s candidate. That would be a major shift for an area where Nigel Farage’s party ousted all but one of the 26 Labour councillors in last month’s local election. 'Vote Andy' stickers on a Reform UK placard in Makerfield. GettyInfoIf Mr Burnham fails to win in Makerfield, that will inevitably trigger a leadership contest. Several MPs are on hand to make a bid. Former health secretary Wes Streeting has already signalled that he has the 80 Labour MPs needed to trigger a leadership contest. Other figures could also stand, such as former deputy leader Angela Rayner and even Al Carns, who resigned as armed forces minister last week, alongside defence secretary John Healey, over a lack of funding for the military. Those resignations almost certainly sealed Mr Starmer’s fate, which is extraordinary considering Labour under his leadership won a huge majority in the 2024 general election.Much will depend on how his cabinet colleagues react to Makerfield. Some have allegedly already asked the Prime Minister to set out a timetable for his departure. It is also understood that Mr Burnham is planning to deliver a private ultimatum to Mr Starmer over the weekend. A crucial date is next Tuesday, when Mr Starmer could face a revolt at the cabinet meeting. As police escorts whisk him away from the lakeside idyll on Lake Geneva, Britain’s current prime minister will almost certainly reflect on the power and privilege that have slipped through his fingers.