Boris Johnson is reportedly urging Conservative MPs to back him for an extraordinary return to Downing Street with a pledge that only he can win the Tories the next election.
Mr Johnson is also pressing Rishi Sunak to reach out and “get back together”, offering an olive branch to the former chancellor after their public falling out at the top of government, reports say.
On Thursday night, Mr Sunak was narrowly ahead of Mr Johnson among Tory MP nominations.
Mr Sunak was leading on 29 Tory MP declarations, followed by 24 for Mr Johnson and 11 for Penny Mordaunt.
Just six weeks after he left No 10 for the final time, forced out by his own MPs after one scandal too many, allies are urging Mr Johnson to run again for a second shot at the Tory crown.
Such a move would be highly divisive within the Conservative Party, with reports that some MPs could resign the whip and sit as independents rather than serve under Mr Johnson.
But his supporters argue that he alone of the candidates to be the new prime minister has won a general election and has a mandate from the British public.
In order to do so, however, he will need to secure the nominations of 100 of the party’s 357 MPs – a target that some at Westminster believe may be beyond him.
Boris Johnson's time as British Prime Minister - in pictures
There was no immediate word from Mr Johnson – who was thought to be holidaying with his family in the Caribbean – on his intentions.
But diehard loyalist Nadine Dorries, the former culture secretary, said she had spoken to him after Ms Truss’s resignation and hinted strongly that he was preparing to run.
“He is a known winner and that is certainly who I’m putting my name against because I want us to win the general election. Having a winner in place is what the party needs to survive,” she told Sky News.
Mr Johnson has put his ability to win elections - he secured the biggest Tory majority for three decades in 2019 - at the heart of his pitch, says The Telegraph.
“If the Tories are serious about winning in 2024 and want to stop a general election before then they need to revert to the guy with a mandate who is a seasoned campaigner," an ally of Mr Johnson told the newspaper.
"They need someone to take the fight to Labour. There’s no point going to a yellow box junction without knowing how you are going to get out of it. Rishi should make contact and work out how the two of them can get back together.”
Boris Johnson through the years - in pictures
Veteran backbencher Sir Roger Gale, a long-time critic of Mr Johnson, warned that if he succeeds he could be met with a wave of resignations by Tory MPs.
“I think that there would be people, indeed like myself, who would find ourselves in the awful position of having to resign the Conservative whip,” he told Times Radio.
Labour leader Sir Keir Starmer, who called for an immediate general election, said the potential return of a man deemed “unfit for office” by his own MPs “adds insult to injury” for voters.
For critics, a comeback would be particularly problematic as Mr Johnson still faces an investigation by the Commons privileges committee over claims he lied to Parliament over lockdown parties in Downing Street, which could see him expelled as an MP.
As well as Mr Sunak and Ms Mordaunt, some MPs would like Defence Secretary Ben Wallace to stand, although he has given no indication he intends to do so.
Other names in the frame include Suella Braverman, who was forced to quit as home secretary by Ms Truss, and International Trade Secretary Kemi Badenoch – both of whom stood in the last contest – although they may struggle to get the nominations.
Boris Johnson applauded in the halls of Number 10 as he leaves - video
Under the rules set out by Sir Graham Brady – the chairman of the Conservatives' backbench 1922 Committee – and party chairman Sir Jake Berry, nominations will close at 2pm on Monday.
The first ballot of MPs will then be held between 3.30pm and 5.30pm on Monday – if there are three candidates with the required number of nominations, the loser will be eliminated.
Once there are two candidates remaining, an indicative vote will be held so that the party membership know which is the preferred option among MPs.
Members will be able to take part in an online vote to choose their next leader and the country’s prime minister with the contest due to conclude by October 28.
The rules appear designed to encourage the candidate who finishes second to stand aside for the winner, ensuring the new leader has the support of the majority.
But few believe that if that is Mr Johnson, who remains hugely popular among ordinary members, he would do so.
Boris Johnson's final PMQs: Most memorable moments - video
Tory grandee Sir Geoffrey Clifton-Brown, however, said it was important that the new leader commanded as much support as possible among the MPs.
“It is the members of Parliament who have to work with a prime minister and I think it is very, very important that as many members of Parliament are satisfied with the candidate,” he told BBC2.
Ms Truss’s resignation on Thursday after just 44 days in office brings to an end the shortest premiership in British history.
It followed weeks of financial and political turmoil after then-chancellor Kwasi Kwarteng’s calamitous £45 billion ($50bn) mini-budget giveaway that led to a collapse in support for Ms Truss among Tory MPs.
