Boris Johnson’s successor won't be announced for two months, but the process to replace him has already begun.
There were 11 candidates, but that's now been cut down by one after Transport Secretary Grant Shapps pulled out of the race and announced he is backing Rishi Sunak.
And the remaining ten will be whittled down to a final two over the next nine days as they battle for the backing of their colleagues.
Tuesday is likely to see some other hopefuls fall at the first hurdle, with several key days over the coming weeks and the new prime minister revealed on September 5.
Here is a breakdown of what is going to happen and when.
Tuesday July 12 - nominations open and close
In order to stand, a candidate will need the support of at least 20 MPs – potentially making it harder for some of the less well-known contenders to make it onto the ballot paper. Ten candidates are in the running for the top job but only two - former chancellor Mr Sunak and minister Penny Mordaunt - are thought to currently have that number.
How does the process to replace Boris Johnson as prime minister work? Robert Peston explains
Wednesday July 13 - first ballot
Any candidate who fails to get at least 30 votes is expected to drop out.
The previous Tory leadership contest in 2019, which had 10 candidates, saw a first ballot threshold of just 17 votes required, with the greater number this time around perhaps reflecting a desire to more quickly whittle down contenders. Thursday July 14 - second ballot
A second ballot will follow on Thursday with further ballots to be held next week until the list of candidates is reduced to a final two – who will then go forward into a postal ballot of party members. Bob Blackman, joint-executive secretary of the 1922 Committee, said the aim was to have the contest down to the final two before the start of MPs’ summer holidays.
He told Sky News: “We’ve got to slim down the list of candidates pretty quickly to two. “And the one thing that we’re committed to do is to achieve getting to two candidates by Thursday July 21. “That means that we’ll hold a succession of ballots over the next few days in order to get to that position.” Sunday July 17 - first debate
Week beginning Monday, July 18 - further ballots
Further ballots will take place in a bid to whittle down the contenders to just two ahead of the summer recess which begins on Thursday, July 21.
Monday July 18 - second debate
Sky News is scheduled to host another debate the following night, hosted by Kay Burley.
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Friday July 22 onwards - campaigns
Hustings are to take place around the country over the summer to help party members determine their choice for the new Conservative leader.
Mr Blackman said it is a “condition of nomination” for candidates to agree that they will contest the ballot of party members if they reach the final two. This is to avoid a situation as in 2016, when Dame Andrea Leadsom dropped out, handing the leadership unchallenged to Theresa May before party members were given the opportunity to vote. Monday September 5 - new Conservative leader announced
The new prime minister will be announced on September 5 when MPs return to Westminster from their summer break.