LONDON (Reuters) - British Prime Minister Theresa May has said she will agree a timetable for the election of her successor after a fourth and final vote on her Brexit deal in parliament early next month.

Britain's Prime Minister Theresa May leaves church near High Wycombe, Britain May 19, 2019. REUTERS/Henry Nicholls

But May is under pressure from members of her own party to step down sooner. A speech to push her new offer to lawmakers on Tuesday appeared to turn more of them against her deal, which has already been rejected three times.

A national election is not automatically triggered if she stands down, instead it is up to her Conservative Party to choose her replacement as party leader and prime minister.

Here is how that process, which is overseen by the party’s 1922 Committee, is likely to work:

CANDIDATES NOMINATED:

Candidates putting themselves forward for the leadership must be nominated by two other Conservative lawmakers. A large number of Conservatives appear to be jostling to replace May so there could be a wide field of candidates.

BALLOT OF LAWMAKERS:

Conservatives lawmakers then hold several rounds of votes to whittle down the number of candidates. Each time they are asked to vote for their favored candidate in a secret ballot, and the person with the fewest votes is eliminated.

This process is repeated until there are two candidates remaining. Votes previously have been held on Tuesdays and Thursdays.

MEMBERSHIP VOTE:

The final two candidates are then put to a postal ballot of the wider Conservative Party membership, with the winner named the new leader. The party had 124,000 members as of March 2018.

There is no fixed time period for this. At the last leadership contest in 2016, this vote was due to last for around nine weeks but did not go ahead after May’s opponent, Andrea Leadsom, pulled out of the race. At the previous contest in 2005, the process took around a month.

WHO IS PRIME MINISTER DURING THE CONTEST?

May would be expected to stay on as prime minister until her successor was chosen although some local media have suggested a caretaker leader could be appointed in the interim.

COULD THE PROCESS BE SPEEDED UP?

If May leaves before a Brexit deal has been approved, it is possible the 1922 Committee could propose a quicker contest in order to get a new leader in place as soon as possible to negotiate with the EU ahead of Britain’s Oct. 31 departure.

Lawmakers could also seek to coalesce around a smaller number of candidates in order to make the process of choosing the final two to put to the membership quicker.