Nigel Farage has vowed to 'throw absolutely everything' at the Makerfield by-election, in what will be the most dramatic and consequential race in over half a century.
This afternoon, former minister Josh Simons said he planned on resigning and sparking a by-election to allow Andy Burnham to make a sensational return to Parliament.
But the Manchester Mayor's route back to the frontline of politics could be upended by Reform UK, who believe they have a very real chance of snatching the seat.
The insurgent right-wing party immediately published numbers suggesting they stormed to victory in the constituency at last week's local election.
Of the eight wards within Mr Simon's seat that went to the polls, Reform UK won every single one and trounced the Labour Party.
Mr Farage secured 50.4% of the vote, compared to Labour's dismal 22.7%.
According to polling experts Britain Predicts, Reform would take the seat if a general election were held tomorrow, clearing Labour by 13 points.
The seat has returned Labour MPs at every election since it was created in 1983, with sizable majorities up until 2019 when Boris Johnson's Tories came within 5,000 votes of taking it.
Nigel Farage has vowed to 'throw everything' at the upcoming by-election
Andy Burnham wants to stand in the constituency, with claims Keir Starmer won't block him for a second time
In 2024, Reform became the local opposition, leapfrogging the Tories and coming just 5,399 votes behind Mr Simons.
Reform UK also believes that they stand a strong chance of winning the Manchester Mayoralty, which Mr Burnham will be forced to vacate if he stands for Parliament.
Across the city's local elections, Reform UK won 234,000 votes to Labour's 177,000 and the Greens' 147,000.
The by-election, should Mr Burnham be allowed to stand as Labour's candidate, is therefore shaping up to be an enormous test of the 'King of the North' and his local popularity.
Mr Burnham confirmed his intention to apply to Labour's National Executive Committee to stand for the seat last night, saying he cares 'deeply about it and its people'.
Making his pitch, he argued: 'There is only so much that can be done from Greater Manchester.
'Much bigger change is needed at a national level if everyday life is to be made more affordable again.
'This is why I now seek people's support to return to Parliament: to bring the change we have brought to Greater Manchester to the whole of the UK and make politics work properly for people.'
He made no references to his ambition to stand for the Labour leadership when back in the Commons, but said Labour figures 'owe it to people to come back together as a Labour movement, giving the Prime Minister and the Government the space and stability they need as the by-election takes place'.
The news was greeted with joy by Labour MPs who are backing Mr Burnham to replace Sir Keir Starmer as Prime Minister.
Among them was Liam Conlon MP, the son for Sir Keir's former Chief of Staff Sue Gray, who said Mr Burnham's announcement was 'good news for the Labour Party and the country'.
He issued a warning to the Prime Minister and others not to block him from standing.
Josh Simons will quit the Commons, allowing Mr Burnham to make a long-awaited return
Jess Phillips warned that Andy Burnham must avoid coming off 'entitled' by thinking he can win any seat
Clive Lewis, the left-wing backer of Mr Burnham who has been leading calls for the NEC to allow him to stand, thanked Josh Simons for the decision to sacrifice his career.
The NEC's decision will be made in the coming days, with the next meeting scheduled for next Tuesday.
But speaking in the wake of Mr Simons's resignation, top Cabinet minister and Starmer loyalist Pat McFadden appeared to dampen expectations that Mr Burnham will be allowed to stand.
Asked directly whether Sir Keir and the NEC will block his candidacy, Mr McFadden told Sky News: 'There are a lot of steps to go here, and a lot of assumptions.
'In the end it is the voters of Makerfield who will decide who the next MP is.
'What [the NEC] will look at is the consequences for the seat and also the consequences for Greater Manchester where Andy Burnham is mayor, and they'll make a decision.'
His fellow Cabinet minister Steve Reed added that while he was 'sorry' that Mr Simons had taken the decision to quit the Commons, 'If anyone thinks there is a caped superhero that is coming our way with all the answers they have another thing coming.'
Meanwhile Jess Phillips, the Home Office minister who resigned this week, warned Mr Burnham not to appear 'entitled' by presuming he can win the seat for his own career goals.
Ms Phillips told the Electoral Dysfunction podcast: 'If there's a sort of level of entitlement that 'I feel like I'll just have X, Y, and Z seat. I don't know - I'm really rooted in the place where I represent.
'And so I always think it doesn't look great at playing a sort of Game of Thrones.'
Following Mr Simons' announcement, the Labour NEC will now write to the whole party informing them that nominations are opening.
Mayors must apply for special permission to stand, with the NEC then meeting to discuss and consider granting it.
If given permission, he would have to apply for the seat in the normal way, including rounds of interviews.
Yesterday (THURS) the Mail reported a senior NEC source who now believes the panel will give Mr Burnham permission to stand, with supporters saying there is a need to 'broaden the debate'.