The leadership contest was triggered last week when Johnson, 58, was forced to step down after a frenzy of more than 50 resignations from his government, in opposition to his scandal-hit premiership.
The influential 1922 Committee of non-ministerial Tory MPs in parliament on Monday outlined a timetable for the party’s leadership election.
Nominations will officially open and close on Tuesday, with a new prime minister set to be installed when parliament returns from the summer break on September 5, Graham Brady, chair of the 1922 Committee, told reporters.
Tory MPs will whittle the current list down to a final two through a series of ballots, with the worst-performing candidate eliminated after each round, before party members choose the winner.
With calls for Johnson to leave Downing Street as soon as possible — and to avoid the process dragging into MPs’ summer holidays — the numbers are likely to be pared down quickly to just two.
The joint-executive secretary of the 1922 Committee, Bob Blackman, said they were committed to doing that before parliament breaks for the summer on July 21.
The first ballot will be held on Wednesday, with a second ballot likely on Thursday, said Brady.
In a bid to speed up the process, candidates must have at least 20 MPs backing them in order to enter the race, up from the usual eight, and any candidate who fails to get the support of 30 MPs in the first ballot will be eliminated.
Among those running are Rishi Sunak and Sajid Javid, whose departures as finance minister and health minister sparked the wave of resignations.
Foreign Secretary Liz Truss and Sunak’s successor Nadhim Zahawi have also declared, and Home Secretary Priti Patel is reportedly mulling a bid.
But a poll of grassroots members by the influential ConservativeHome website released on Monday showed strong support for less high-profile candidates, with former defence minister Penny Mordaunt holding a narrow lead from arch-conservative Kemi Badenoch.
Brexit figurehead Johnson dramatically announced his departure as party leader last Thursday but is staying on in Downing Street until a replacement is found.
Javid said that with Britain facing a soaring cost-of-living crisis, energy price hikes and the war in Ukraine, there was a need more than ever for “competence” in the country’s leaders.
“I’ve every hope that this campaign can and will be the turning point that we need,” he said at a campaign launch.
– Fall from grace –
On a visit to a science research institute in London, Johnson was asked directly if he would endorse any of the candidates, six of whom are from black and minority ethnic backgrounds.
“The job of the prime minister at this stage is to let the party decide, let them get on with it, and to continue delivering on the projects that we were elected to deliver,” he said.
Johnson’s fall from grace has been spectacular. In December 2019 he won a landslide 80-seat victory on a promise to take Britain out of the European Union.
His parliamentary majority allowed him to do just that but his premiership was hit by waves of scandal, not least about lockdown-breaking parties in Downing Street that saw him fined by police.
Another row blew up last week about his appointment of a senior colleague despite knowing of sexual assault allegations against him, sparking the government resignations.
In his speech, he blamed the “herd” for moving against him, and his allies have been briefing angrily against Sunak.
But Johnson refused to say Monday whether he felt betrayed.
“I don’t want to say any more about all that,” he said.
“There’s a contest under way and that has happened and you know, I wouldn’t want to damage any chances by offering my support.
“I just have to get on and in the last few days or weeks… the constitutional function of the prime minister in this situation is to continue to discharge the mandate. And that’s what I’m doing,” he added.
“The more we focus on the people who elect us… (and) the less we talk about politics at Westminster, the generally happier we will all be.”