Here we go. Sir Keir Starmer today declared he will take on Andy Burnham, or anyone else, in a battle to be leader of the Labour Party.
Asked if he was “determined” to take part in any future contest, Sir Keir told the BBC: “Well, I don’t think it should happen, but if it does, then I will fight.
“And let me just be clear with you. That’s not about personal vanity.
“It’s not about stubbornness. It’s out of a very deep sense of duty.
“I was elected to serve this country notwithstanding the difficult circumstances; that is what I am doing.”
The remarks came at the end of another difficult week for the Prime Minister, with both Defence Secretary John Healey and Armed Forces Minister Al Carns quitting over defence spending.
This week, for the first time in Sir Keir’s turbulent premiership, I felt that the lawyer-turned-politician might not survive this challenge to his leadership.
The Prime Minister has built his premiership on being the steady pair of hands, ready to rise to meet the various threats facing the UK in an increasingly unstable world.
So, it was a surprise in Westminster when Mr Healey and Mr Carns resigned over defence spending.
Sir Keir wants to raise it by £13.5billion, when the military top brass want £28billion.
Mr Healey was excoriating in his resignation letter on Thursday, saying: “You have been unable, and the Treasury has been unwilling, to commit the resources that the nation needs to defend the country.”
A more political Prime Minister might have sided with Mr Healey and forced out his Chancellor, Rachel Reeves, in the fight.
In fact, one Government source admitted they thought Ms Reeves was going to resign instead.
Yet, that is now how Sir Keir likes to run things.
Not for nothing does his team in No10 fret that he lacks the political nous necessary to win these kinds of battle.
Sir Keir seems to be building his case for survival around the case that the same challenges facing him now will have to be dealt with by his successor.
And will they be any better?
He has a point.
Andy Burnham, the favourite to succeed Sir Keir in No10, seems to be flip-flopping all over the place on policies.
Most recently, the Greater Manchester Mayor was forced to U-turn on whether he wants to fund payouts to so-called Waspi women.
So far, his successors have never faced the level of scrutiny Sir Keir is going through.
And it may well be that a political fight to survive – when he can work out what he believes in and communicate that to the country – is just what he needs to reboot his premiership.
It has to be, because otherwise it is over.