Andy Burnham has been forced to come clean about his leadership ambitions because the view of Sir Keir Starmer’s Labour Party on the doorstep has become so “toxic” that the Makerfield by-election is still “too close to call”, his allies say.After weeks of speculation, the Greater Manchester mayor used his appearance on a BBC Question Time by-election special on Thursday night to finally confirm that he would run to replace Sir Keir as Labour leader and prime minister if voters in Makerfield send him back to Westminster when they go to the polls later this month. While new polling suggests Mr Burnham may be pulling away from his chief rival for the seat, Reform UK’s Robert Kenyon, his allies remain concerned that the Manchester mayor’s position as the Labour candidate could still leave him at risk of defeat, given the party’s low poll ratings. One ally suggested that Mr Burnham's answer on his leadership ambitions was a deliberate strategy to distance himself from the current Labour leadership and give himself the best chance of winning the by-election.The MP said: “Focus groups show nothing less will cut through the Labour brand toxicity. ‘Changing Labour’ isn’t explicit enough. That was.”Burnham used his appearance on BBC Question Time to declare that he would run for the Labour leadership (Reuters)Reflecting on what people in Makerfield are saying on the doorsteps, the MP added: “The Labour brand is not just bad, it’s toxic.“Andy isn’t toxic. Labour is. That's the only reason we might just get over the line.”Another ally, Liverpool Riverside MP Kim Johnson, who was at Mr Burnham’s by-election campaign launch and will return next week, said: “The thought of getting rid of Starmer would benefit him [Burnham].”York Central MP Rachael Maskell, who has been to the constituency four times said: “There is a lot of support for Andy in the light that he would always see the country through his experience of growing up and living in the area and then representing Makerfield. The local community have a real opportunity to help shape the future, and I know Andy is keen to move more power out of Westminster, so voting for him would be their best chance to sweep in the change they want to see.”Robert Kenyon attacked career politicians on BBC Question Time (BBC)Another Labour MP who was recently in the seat campaigning added: “Andy’s promise to run for the leadership will motivate a lot of people given Starmer’s lack of popularity!”It comes amid continued nervousness about the result of the vote on 18 June in the constituency, with Labour figures admitting that attacks on Reform candidate Robert Kenyon’s colourful social media history and past misogyny have not shifted the dial in the constituency.One Labour MP said: “It’s like we didn’t learn the lessons of Brexit a decade ago. ‘Project sneer’ about the local guy plays well in the national media but has little impact in Makerfield, where people know him [Kenyon].”Polling suggests that Mr Burnham may be pulling away from his rival with A poll by Survation immediately after the Question Time debate gave Mr Burnham he had a 10-point lead over Mr Kenyon, but his slender lead has led Labour to hope that Rupert Lowe’s rival party, Restore Britain, will take enough votes off Reform to split the rightwing vote.The Survation poll suggests that Restore’s candidate Rebecca Shepherd, who was controversially left off the BBC Question Time panel, is on 8 per cent.One Labour source said: “Restore could make the difference in this by-election. The numbers are that tight. Really too close to call.”An experienced campaigner in Reform involved in the by-election campaign believes that Mr Kenyon’s pitch as “the local man who knows everybody” means the contest is “very close”.Starmer has insisted he will fight a leadership election (Getty)Sources in both parties have admitted that if Mr Burnham was not the Labour candidate then Reform would easily win the seat. There are no precise figures on how the parties performed in Makewrfield during the local elections, but Mr Farage’s party gained 24 out of 25 seats on Wigan Council – including in two wards in Ashton-in-Makefield – last month.The Reform source noted: “Robert gets a warm welcome wherever he goes. It is obvious the fact that this is a local guy wanting to represent his home town against the man who wants to use it to become prime minister is playing well for us.”Issues like Mr Farage’s push on “two tier” policing in the wake of the Henry Nowak case and the mishandling of it by the police who thought arrested the 18-year-old over false allegations of racism while he bled to death is also having an impact.The source said: “It plays into a deeper feeling of how communities like Makerfield have been ignored and how white working class people are discriminated against. Immigration is a big issue for us as well.”Meanwhile, Sir Keir has defiantly held out against Mr Burnham and other contenders’ ambitions.In response to Mr Burnham’s declaration on Thursday night, a Downing Street spokesman said: “With Keir Starmer’s leadership, this Labour government is supporting people with the cost of living, cutting NHS waiting lists, restoring control of our borders and lifting half a million children out of poverty.“The country expects us to focus on governing and to deliver change for hardworking people, not get distracted by Westminster debates.“The Labour Party has a process for challenging a leader and it has not been triggered. The Prime Minister will not walk away from the mandate he was given just two years ago to build a stronger, fairer Britain.”