RISHI Sunak and Boris Johnson are in a tight-race for No10 as frontrunners send out the troops to round up MPs.
The former PM and ex-Chancellor are both vying for the top spot after Liz Truss sensationally quit after just 44 days in the top job.
Boris Johnson is eyeing the mother of all political comebacks after Liz Truss resigned
Rishi Sunak is also understood to be in the running
But Tory chiefs said candidates would need the backing of at least 100 MPs to have any chance of going to a ballot of party members.
Johnson was installed as one of three favourites — with Mr Sunak and Penny Mordaunt — and took an early lead with at least 44 Tory MPs getting behind him.
Tory chiefs, including 1922 Committee chair Sir Graham Brady, yesterday said candidates need to be nominated by 100 MPs — a threshold which Boris supporters fear he might struggle to meet.
And Tory MP Marco Longhi said: “I am backing Boris and as a democrat it’s important that members have their say.
“He is the only person that commands that authority given to him by the public at a General Election. Please come back, Boss.”
Allies of Boris said he could form a potent partnership with Mr Sunak — with Boris as the successful campaigner and his ex-neighbour as his deputy, stabilising the economy.
The pair would have to make peace after months of feuding, which also saw Boris back Ms Truss for the leadership.
But friends of Mr Sunak say that, while he wants to bury the hatchet, he aims to become PM so he can get on with the task of rebuilding the battered economy.
BoJo is expected to cut short a Caribbean holiday to win backers, less than seven weeks after he walked out of Downing Street.
Allies including his “Mr Fixit”, MP Nigel Adams were last night making frantic calls to build his support base, believing he is the only candidate who can avoid a wipeout at the next election.
Mr Johnson faces an uphill battle for the top job against Mr Sunak plus Commons Leader Ms Mordaunt and Defence Secretary Ben Wallace.
Former candidates Kemi Badenoch and Suella Braverman are considering whether to run again.
Boris-backer Tory MP James Duddridge said: “I hope you enjoyed your holiday, Boss. Time to come back. Few issues at the office that need addressing.”
This morning, Boris Johnson’s dad Stanley said he thinks the ex-PM is “on a plane” back to Britain.