The Conservatives are scrambling to elect a new leader this week, with a new prime minister promised on Friday.
It is just seven weeks since Liz Truss won the party’s latest leadership election after Boris Johnson resigned amid a series of scandals.
However, Mrs Truss was forced to resign last Thursday after markets rejected her mini-budget.
Sir Graham Brady, chairman of the powerful 1922 Committee of Conservative MPs, said the election process would end on October 28, so the new leader would be in time for a crucial financial statement on October 31.
Sir Graham said the parliamentary stage of the contest had begun last Thursday afternoon, with nominations open.
what will happen on monday
The parliamentary stage of the Conservative leadership contest will conclude on Monday.
Candidates will need a minimum of 100 colleagues to nominate them to proceed to the vote.
“We have set a high threshold, but a threshold that should be achievable by any serious candidate who has a chance of passing,” Sir Graham said.
He said it would mean a maximum of three candidates on the ballot for MPs to vote on, but only two remain – Rishi Sunak and Penny Mordaunt.
If there had been three, the candidate with the fewest votes after the first ballot would have been eliminated on Monday afternoon after a vote in the Commons.
If Mordaunt does not reach 100 votes at 2 p.m
Penny Mordaunt has until 2pm to reach 100 Tory MPs.
As of early Monday morning, he still had less than 30 colleagues who had come out publicly to support him.
If he does not reach this figure, Rishi Sunak will automatically become the new British Prime Minister.
If the increased number of MPs supports Sunak, it would mean the end of Mordaunt
There are two figures to watch out for.
If Rishi Sunak gets 179 public supports, it will mean he has a majority among Tory MPs.
This does not mean that Penny Mordaunt is leaving the race, because in theory she could still accumulate the necessary 100 followers.
However, if Sunak reaches 258, it will be the end of the road for his only rival, as it would mean just 99 Tory MPs would remain.
If MPs rally around Mordaunt to reach the benchmark
Penny Mordaunt has insisted she is still in the running, and if she manages to pick up Boris Johnson’s leftover votes to reach 100, then she and Rishi Sunak will go head-to-head.
Around 2.30 pm there will be a call to Parliament, which will give each candidate the opportunity to present their case to parliamentarians.
Then, in a procedural change from the last leadership contest, an “indicative” vote will be held.
This will be held in the Common between 18.30 and 20.30 hours on Monday, and the result will be announced at 21.00 hours.
The hope among some is perhaps that the loser of the “indicative” vote may drop out of the race, in which case a new leader emerges without the involvement of Conservative party members.
When David Cameron stepped down, the leadership contest was not voted on by party members as Theresa May was left unopposed after Andrea Leadsom withdrew from the race.
If neither is abandoned, this final vote by MPs will allow Conservative MPs to know – which they did not do in the last election – the preferred of the two parliamentary party candidates, which could dissuade them from choosing the other
What happens after the vote of the deputies?
If it ends up being two candidates, Conservative members across the country who joined the party at least three months ago will have their say.
Conservative party chairman Sir Jake Berry said: “We have decided that if the party decides to field two candidates, there would be an online, binding and accelerated vote by Conservative Party members to choose their next leader.”
Voting will close at 11am on Friday 28 October, with the result announced later that day.
Will there be boxes?
Sir Jake said Conservative HQ would work with broadcasters to organize a streaming event so members could hear the final two candidates before voting.
However, no boxes have been announced.