As Jeremy Corbyn signals he could quit as Labour leader in the early part of next year, after a bruising General Election defeat, here is a look at how any upcoming leadership contest could play out.
How is a leadership contest triggered?
Mr Corbyn has said it is for the party’s ruling National Executive Committee (NEC) to set the timetable for a leadership contest, expected to be some time in early 2020.
The Labour Party rule book states that if the party leader is no longer available, the deputy leader automatically becomes leader on a temporary basis.
The NEC would then decide whether to hold an immediate postal ballot for a new leader, or to wait until the next party conference.
But as deputy leader Tom Watson stepped down shortly before the election was called – and so both leader and deputy are unavailable – the NEC then conducts a postal ballot of Labour membership to select a new leader.
In the interim period, the NEC may appoint a temporary leader.
How can someone be nominated?
A candidate needs the support of 10% of MPs and MEPs and, in a rule introduced in 2018, candidates also need nominations from at least 5% of Labour’s constituency parties, or from at least three affiliates which represent a minimum of 5% of the affiliated membership. Two of the affiliates must be trade unions.
Affiliate groups are organisations such as trade unions or socialist societies.
Who can vote?
Members of the Labour Party, affiliated trade unions and registered supporters are able to vote in a leadership contest.
The party has used a one-person-one-vote system since 2015. In the postal ballot voters rank candidates in order of preference and, if more than half of voters have the same favoured candidate, they are elected.
If there is no overall winner, the candidate who came last is removed and votes are redistributed to the voters’ next preference, repeating the process until a winner is produced.
Who are the runners and riders?
Shadow chancellor John McDonnell played a prominent role throughout the General Election campaign, but appeared to rule himself out as future leader on Thursday night.
Emily Thornberry, shadow foreign secretary, has deputised for Mr Corbyn at Prime Minister’s Questions and is perceived as one of the front runners should an election contest be called.
Sir Keir Starmer is another member of the shadow cabinet tipped to replace Mr Corbyn, alongside shadow education secretary Angela Rayner and shadow business secretary Rebecca Long-Bailey.