Britain could have a new prime minister as early as Monday afternoon.
Candidates had to reach a high bar of 100 supporters among Tory MPs to get to the first round of voting.
With a total of 357 MPs in the British Parliament, this means a maximum of three can stand. Former chancellor Rishi Sunak has announced his candidacy alongside Leader of the House Penny Mordaunt.
Former prime minister Boris Johnson collected support but never officially hit the threshold of 100 and pulled out of the race.
Hopefuls have until 2pm UK time (5pm UAE) on Monday to submit their nominations of more than 100 MPs.
The decision to elect the next party leader, and therefore prime minister, then ends with a vote of the 166,000 Tory party members, if two candidates get enough support to qualify.
The members will vote online for their preferred candidate, with the winner announced on Friday.
If members have to choose between two candidates, there will be at least one live broadcast debate.
But it was confirmed by Sir Graham Brady, chairman of the 1922 Committee that sets the rules, that if one of the final pair of candidates were to drop out of the race on Monday, the remaining person would instantly become party leader.
Liz Truss, the current prime minister, would then see King Charles III to offer her formal resignation. The new leader would also have a formal audience with the king.
How is a new leader elected?
Nominations close on Monday at 2pm (5pm UAE). The result is expected soon after.
Candidates must have support from at least 100 of the party's 357 MPs to continue.
If there is only one candidate, the contest is over.
If there are two candidates, then the final choice will go to a vote of party members.
The initial contest rule allowed for three MPs to reach the threshold of 100 but, barring a major surprise, that will not happen.
Party members will vote between Tuesday and Friday. The ballot closes at 11am Friday, with the result announced soon after.
