Nominations will close today in the battle to succeed Harriet Harman as the next deputy leader of the Labour Party.
Former ministers Caroline Flint and Tom Watson have already secured enough support from fellow MPs to make it on to the ballot paper.
Contenders hoping to join them include Ben Bradshaw (Exeter), Stella Creasy (Walthamstow), Rushanara Ali (Bethnal Green and Bow) and Angela Eagle (Wallasey).
On latest figures, Mr Watson was the front runner in the contest with the backing of 59 MPs, including former chief secretary to the Treasury Liam Byrne and shadow defence secretary Vernon Coaker.
Ms Flint's 41 supporters include former Public Accounts Committee chairman Margaret Hodge and shadow foreign secretary Hilary Benn.
It comes after the Parliamentary Labour Party earlier this week backed four candidates to go forward in the campaign to replace Ed Miliband.
Veteran left-winger Jeremy Corbyn became the surprise addition on the ballot paper after a last-minute surge of MPs agreed to put their name to his candidacy.
Although many made it clear they ultimately will not vote for him, the MPs said they wanted to ensure there was a broad debate about the party's future direction.
He joins shadow health secretary Andy Burnham, shadow home secretary Yvette Cooper and shadow health minister Liz Kendall in the contest, which will involve a series of public and televised hustings over the coming weeks.
The leadership contenders will go head to head in a live television showdown tonight broadcast by BBC2's Newsnight from Nuneaton - one of several target seats Labour failed to win in the general election that will host hustings.
Other programmes, to be broadcast by Channel 4, Sky News, The Sunday Politics, BBC Radio 5 live and LBC radio, will come from towns such as Stevenage and Swindon.
The eventual winner - selected by a one member, one vote system which replaced an electoral college that gave extra weight to politician and trade union choices - will be announced at a special conference on September 12.