Top Tory Ben Wallace today ruled himself out for Prime Minister - and announced he is set to back Boris Johnson.
The Defence Secretary had been tipped to run in a lightning-quick Tory leadership race, where candidates need 100 MP backers by 2pm on Monday.
But today Mr Wallace, who led Boris Johnson's aborted 2016 campaign, announced: "I am not going to be standing for Prime Minister this time."
And as Mr Johnson attempts to mount a surprise comeback with claims he'll reach 100 MP backers, he said: "At the moment I would lean towards Boris Johnson."
He admitted the ex-PM still had "questions to answer", including giving evidence within weeks over whether he lied to Parliament over Partygate. But he said the party needs someone who can "win elections".
It makes him the second Cabinet minister after Jacob Rees-Mogg to back Mr Johnson, who is being touted for a sensational return to No10 after returning from his extended Caribbean holiday while Parliament sits.
The Defence Secretary is popular with MPs and the party’s grassroots, consistently topping the Cabinet league table run by Tory bible ConservativeHome.
The 52-year-old, who has been an MP since 2005, was widely praised for his response to Russia's invasion of Ukraine.
The privately-schooled son of a soldier attended Sandhurst and served in Germany, Cyprus, Belize and Northern Ireland before entering politics in the early 2000s, including as an aide to Ken Clarke.
Mr Wallace told Sky News: “I have to recognise the issue of the mandate. This will be potentially our third Prime Minister since the general election.
“That means we have to think about that legitimacy question the public will be asking themselves, and also about who could win the next election.
“So at the moment, I would lean towards Boris Johnson. I think he will still have some questions to answer around, obviously, that investigation.
"But I know when I was Defence Secretary he invested in defence, he supported me, he supported the actions this country has taken to keep us safe.
"So at the moment I'm leaning towards that, but there are a few days to go, and we'll see what happens."
Tory chiefs have fired the starting gun on the second leadership contest in a matter of months following the dramatic collapse of Ms Truss's premiership in just six weeks.
A new Prime Minister could be announced as early as Monday night or Tuesday morning if only one candidate emerges - or by Friday if there is a contest between two rivals.
Supporters of Mr Johnson immediately started calling for the scandal-ridden former PM to make an extraordinary comeback, only months after he was forced to quit by his own MPs.
Business Secretary Jacob Rees-Mogg was among MPs tweeting a new graphic with the slogan: 'Boris or Bust'.
Mr Johnson could find himself up against his bitter rival - and his former Chancellor - Rishi Sunak, as well as Commons Leader Penny Mordaunt who is gathering early support.
More than 40 MPs have come out for Mr Sunak, with around 35 publicly backing Mr Johnson and some 15 supporting Ms Mordaunt.
Labour demanded an immediate general election, with Shadow Chancellor Rachel Reeves saying No10 and No11 are not a "short term AirBnB".
Critics said there would be a "wave of revulsion" if the controversial former Tory leader returned to Downing Street.
A return to power for Mr Johnson would be hugely divisive in his own party, with some Tory MPs saying they would quit rather than serve under his leadership.
Mr Johnson still faces a Commons probe over claims he lied to Parliament about lockdown boozing in Downing Street, which could potentially see him expelled as an MP.
A Cabinet Minister told Sky News that Mr Johnson could get the backing of more than 100 MPs - the threshold needed to get on the ballot paper.
"Even people who resigned from his government were on the terrace yesterday telling colleagues they would now back him and members definitely will," the unnamed Minister said.
The Ukrainian Government appeared to throw its weight behind Mr Johnson.
The official Twitter account posted a meme based on the Netflix show Better Call Saul, with a photo of Boris Johnson's face, saying "Better Call Boris."
But Sir Roger Gale, a long-time critic of Mr Johnson, warned that he could be met with a wave of resignations by Tory MPs.
Conservative MP Tim Loughton publicly attacked Mr Rees-Mogg for tweeting the slogan 'Boris or Bust'.
He tweeted: "Jacob-how on earth can that slogan be remotely helpful to the Party given the strong possibility that the next PM will not be Boris?
"I would not use the tag line #BorisandBust and you really should think this through properly if you have any interest in party unity."
