Tory party chiefs have moved to speed up the contest to replace Liz Truss by requiring candidates to have the support of 100 MPs to enter it.
The threshold – much higher than the 20 nominations needed last time – could also keep Boris Johnson out of the race, after he signalled his hopes of making a sensational return.
If only one MP gains 100 nominations, they will become prime minister immediately, with no contest.
Many Tories are hoping for such a “coronation” to prevent party members having a say on the next leader – but Rishi Sunak, Penny Mordaunt, Suella Braverman, Kemi Badenoch and others are ready to run.
“We fixed a high threshold but a threshold that should be achievable by any serious candidate who has a prospect of going through,” chair of the 1922 Committee, Graham Brady, said.
The high threshold makes make it easier to coalesce around a unity candidate because a maximum of three names out of 356 Tory MPs can qualify.
A unity candidate could emerge as early as Monday, when nominations close at 2pm.
If there is a contest, the first ballot will be held on Monday between 3.30pm and 5.30pm on Monday with the result announced at 6pm. If a second ballot is needed, it will be held immediately afterwards, between 6.30pm and 8.30pm, with the result announced at 9pm on Monday night.
If there is still a contest, grassroots Tory members would then choose online during next week, with the overall result declared on the afternoon of Friday, 28 October.
Party chair Jake Berry said he will be working with broadcasters to arrange one broadcast hustings, so members can hear from the final two candidates before they vote.
Mr Johnson still faces an inquiry into whether he lied to parliament in the Partygate scandal, but wants to “finish the job” he started, a key ally said.
The Tories need someone who can “bring people together” and who – unlike any other candidate – has “that mandate from the last general election”, Brendan Clarke-Smith argued.
“The only person I think who ticks all those boxes is Boris Johnson,” Mr Clarke-Smith said, adding: “He is the only person who can dig us out of this mess.
“He wants to be able to finish that job – so, yes I think he would be interested and that is why I am urging him now to put his name forward.”
His fellow Conservative MP, James Dudderidge, tweeted under the hashtag #bringbackboris, saying: “I hope you enjoyed your holiday Boris. Time to come back. Few issues at the office that need addressing.”
