Labour members will get their first chance to grill the five MPs standing to succeed Jeremy Corbyn as party leader at an event in Liverpool later.
Rebecca Long-Bailey, Emily Thornberry, Sir Keir Starmer, Lisa Nandy and Jess Phillips will all make their pitch to the party faithful.
The hustings is the first in a series of events across the country before the next leader is elected on 4 April.
Those running to be deputy leader will also face party members.
Candidates Rosena Allin-Khan, Dawn Butler, Richard Burgon, Ian Murray and Angela Rayner will answer questions in a separate hustings later on Saturday.
The hunt for a new Labour leader was triggered when Mr Corbyn stepped down following the party’s fourth general election defeat in a row.
The hustings follows the campaign launches of shadow business secretary Mrs Long-Bailey and shadow foreign secretary Ms Thornberry on Friday.
Mrs Long-Bailey promised to “shake up” how government works and end the “gentlemen’s club of politics” by moving power out of London.
Pledging to “sweep away the House of Lords”, she said she would replace it with an elected senate outside of the capital.
The MP for Salford and Eccles received a boost ahead of her campaign launch when she secured the support of the grassroots organisation Momentum on Thursday.
Ms Thornberry, who scraped through the first stage of the race securing the required amount of support from MPs minutes before the deadline, highlighted her experience challenging Boris Johnson.
She drew attention to her role “on the front line in the fights against climate change, universal credit and anti-abortion laws in Northern Ireland”.
She also said that if she ever lost the confidence of colleagues or thought she was going to lose an election she would stand down.
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The remaining three candidates – Ms Nandy, Ms Phillips, and Sir Keir – have already launched their campaigns.
Setting out her stall, Ms Nandy pledged to abolish tuition fees, renationalise Royal Mail and renew Trident – Britain’s nuclear deterrent – “if it was coupled with a strong commitment to multi-lateral disarmament”.
She also said she did not support another Scottish independence referendum, saying: “I think this country has had enough of referendums.”
Ms Phillips, who launched her campaign in Grimsby – a former Labour seat lost to the Tories in the 2019 election – told supporters “something has to change”, and promised to “truly speak truth to power”.
She called for the creation of a universal childcare service, based on provision in some Scandinavian countries.
Sir Keir, who won the backing of most MPs and MEPs in the first phase of the contest, vowed to restore trust in Labour “as a force for good and a force for change”.
Running under the slogan “another future is possible”, he has pledged to unify the party and end factional infighting.
Sir Keir refused to say whether his politics were closer to Tony Blair or Jeremy Corbyn, saying: “I want to lead a Labour Party that is trusted enough to bring about fundamental change.”
In order to make the final ballot, each of the Labour leadership hopefuls must secure the backing of unions and local parties.
The five contenders need the support of 5% of local parties or at least three affiliates – two must be unions – by 14 February to make the final ballot.
Members of the public who join the party or become affiliated supporters before 20 January will be eligible to vote in the contest.
A YouGov poll of 1,005 Labour members for the Times on Friday suggested Ms Thornberry would go out in the first round of voting with just 3%, with Ms Nandy knocked out in the second round and Ms Phillips in the third, with most of her second preference votes going to Sir Keir.
The poll – which only includes full Labour members, and not others who are entitled to vote – indicates Sir Keir would beat Mrs Long-Bailey in the final round by 63% to 37%, once the other candidates have been eliminated.
It suggests Angela Rayner is on course to win the deputy leadership election in the first round with 57%.