Just three candidates remain in the race to become Labour's next leader, with party members due to start voting on 24 February.
There is a big task ahead for the successor to Jeremy Corbyn, as they will need to bring the party back from its worst electoral defeat, in terms of House of Commons seats, since 1935.
We'll find out who gets the top job on 4 April.
But for now, here are the hopefuls:
Who is running for Labour's leadership?
The 57-year-old shadow Brexit spokesman was the first to qualify for the members' ballot, doing so with the support of unions and affiliate groups.
To qualify, candidates needed support from three such groups representing 5% of the membership, or 33 constituency Labour parties (CLPs).
In total, he received nominations from 15 groups and 370 CLPs - more than any other candidate in both categories.
He qualified for the first round of the contest with nominations from 88 MPs and MEPs, also more than his rivals.
Among his notable backers are transport union the TSSA, and Unison, the UK's largest trade union.
A supporter of remaining in the EU, Sir Keir was director of public prosecutions before becoming MP for Holborn and St Pancras in 2015.
But critics have accused him of pushing Labour into its "renegotiate then referendum" Brexit position ahead of the 2019 election.
The 40-year-old MP for Wigan became the second candidate to qualify for the members' ballot with nominations from four unions and affiliate groups.
Among her backers are the GMB union, the National Union of Mineworkers and the Jewish Labour Movement.
She also secured support from 70 local Labour party branches. She was nominated by 31 Labour MPs and MEPs in the first round.
Ms Nandy worked in the charitable sector before entering politics in 2010, and became one of a clutch of shadow ministers who resigned from Jeremy Corbyn's frontbench after the Brexit referendum.
She has become known for her support of smaller towns, saying the party needed to appeal to voters outside big cities if it wanted to win at the next election.
Ms Nandy declared her bid for leader in a letter to the Wigan Post, saying the loss to Boris Johnson's Conservatives had been "a long time coming" and she had a "deeper understanding of what has gone awry" than her rivals.
The 40-year-old shadow business secretary was the last of the remaining three candidates to secure her place on the members' ballot.
She garnered support from seven affiliates and unions, as well as 160 constituency Labour parties.
During the initial stage of the contest, she received the second highest number of nominations from her colleagues, with the backing of 33 MPs and MEPs.
As well as backing from the Communication Workers Union, she is being supported by trade union Unite, Labour's biggest donor at the 2019 election.
One of a new generation of MPs on the left of the party, she formed part of Mr Corbyn's inner circle and represented Labour in an election TV debate.
She is widely regarded as the preferred candidate of Mr Corbyn and his shadow chancellor, John McDonnell. But critics of the current leadership have accused her of representing "continuity Corbyn".
Who's out of the contest?
Shadow foreign secretary Emily Thornberry was eliminated from the race in mid-February after failing to secure enough nominations from groups or local branches.
She had managed to receive support from 31 CLPs - just two short of the required 33.
Birmingham Yardley MP and outspoken Corbyn critic of Jess Phillips withdrew from the race in January, having failed to secure any union, affiliate or constituency endorsements.
Earlier in the contest, shadow Treasury secretary Clive Lewis withdrew from the race less than an hour before nominations closed, with only five MPs backing him.
What about the deputy leader?
The post has been vacant since the election, when former Labour MP Tom Watson said he was stepping down, both from the role and as an MP.
This means it is now up for grabs, with the winner chosen in a separate contest.
Shadow education secretary Angela Rayner, shadow justice secretary Richard Burgon, shadow equalities minister Dawn Butler, Scotland's only remaining Labour MP Ian Murray and Tooting MP Rosena Allin-Khan are in the running.
All five contenders have made the final ballot, after first getting the required support from MPs and MEPs and then the backing of the required number of local branches or union and affiliate groups.
Ms Rayner - who was a care worker and Unison official before becoming an MP - received the endorsement of her flatmate and friend Mrs Long-Bailey. She has also received backing from seven unions and affiliate groups including Unison, the Union of Shop, Distributive and Allied Workers (USDAW) and GMB.
Mr Burgon - a supporter of Mr Corbyn who has pledged to continue the current leader's policy agenda - has the backing of the Bakers, Food and Allied Workers Union, the Fire Brigades Union (FBU) and Unite.
Ms Butler has only one affiliate nomination - Chinese for Labour - but she has met the threshold by gaining the backing of at least 33 local branches.
Mr Murray also has one affiliate nomination - Labour Movement for Europe - and he made the final ballot by gaining support from the required number of local branches.
Dr Allin-Khan has gained the required support from local branches.
What is the timetable?
Who can run?
Candidates for leader and deputy leader have to be MPs, and they required nominations from 10% of Labour MPs and MEPs to get onto the ballot.
In a new rule, candidates also need nominations from 5% of Labour's constituency parties.
Alternatively, they need nominations from three affiliated bodies, two of which must be trades unions, adding up to 5% of affiliated members.
Who can vote?
Members of the Labour Party, affiliated trades unions (if they opt in), and socialist societies such as the Fabians, all get one vote each.
Those who joined the party or become affiliated supporters before 20 January will be eligible to vote.
Registered supporters - who are not full party members - had 48 hours from 14-16 January to secure a vote by paying £25.
How does the vote work?
They are cast on a one-member, one-vote basis.
Voters fill in a preferential ballot, meaning they rank the candidates in order of preference.
If any candidate gets more than half the first preference votes, they win.
If not, the candidate with the fewest votes is eliminated, and their second preference votes are redistributed.
If that results in any candidate with more than half the votes, they win. If not, the remaining candidate with the fewest votes is eliminated and their votes redistributed, until the contest produces a winner.
Who controls the process?
Labour's National Executive Committee has 39 members, representing the trades unions, the shadow cabinet, Labour's elected representatives at local, national and European level, and constituency parties.
Supporters of Jeremy Corbyn and the grassroots campaign group Momentum are strongly represented on the NEC, and they are likely to use their influence to promote a left-wing candidate in the coming election.