The Conservative Party is trying to end a period of extreme political turmoil by setting a high threshold for candidates trying to succeed Liz Truss, meaning the UK could have a new prime minister as soon as Monday.

Contenders will need the backing of 100 Tory legislators just to get on the ballot, Graham Brady, the member of Parliament who heads the panel that sets rules on leadership contests, told reporters on Thursday. There are 357 Conservative MPs, so a maximum of three of them will be able to run.

Nominations close on Monday, when the ballot necessary to whittle the field down to a final two will also be conducted, Brady said. An indicative vote will then be taken among MPs, before the candidates are put to grassroots members in a deciding online ballot, with the result due to be announced on October 28.  

The outcome of the first ballot of MPs will be announced at 6pm on Monday. If an informal vote is needed, the result would be announced at 9pm. 

In reality, the loser of the informal vote is likely to face enormous pressure to pull out, meaning grassroots members wouldn’t get a say and the contest would be over.

Truss said on Thursday she was quitting as prime minister after a tumultuous and brief period in office in which she announced an economic package that roiled the financial markets, forcing her to fire her finance minister and reverse most of her planned tax cuts. By next Friday, she’ll have served for 52 days — the shortest ever period in office for a British premier.

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Candidates trying to replace her are likely to include former Chancellor of the Exchequer Rishi Sunak — runner-up to Truss in the last leadership contest. Other contenders likely to enter the fray include Penny Mordaunt.

Trade Secretary Kemi Badenoch is “seriously considering” running, according to her spokesperson. Justice Secretary Brandon Lewis is sounding out colleagues over his chances, according to a person familiar with his thinking.

Former Home Secretary Suella Braverman, who Truss fired on Wednesday, may also be in the running. Defence Secretary Ben Wallace is often touted — though he has downplayed his interest.

But Chancellor of the Exchequer Jeremy Hunt, promoted from the back benches after Truss sacked Kwasi Kwarteng in a bid to restore calm in financial markets, won’t be running, according to his spokeswoman.

Grant Shapps, who replaced Braverman as home secretary, also appeared to rule himself out, saying on Twitter: “I will remain fully focused on the job as we select the next PM.” DM