Huw Lewis, Edwina Hart and Carwyn Jones will be in competition
Nominations have closed in the race to replace Rhodri Morgan as Welsh Labour's leader, with confirmation that three candidates will run.
Health Minister Edwina Hart, Counsel General Carwyn Jones and Merthyr AM Huw Lewis are on the ballot paper.
The winner will also follow Mr Morgan as first minister.
Voting by Welsh Labour members, local parties, affiliated groups, MPs, AMs and its MEP will end on 26 November, with the result on 1 December.
Mrs Hart's camp has announced that former Welsh Secretary Paul Murphy is backing her.
BBC Wales correspondents say Mrs Hart's camp hope that will give the lie to persistent suggestions that she lacks support among MPs.
AMs WHO HAVE NOMINATED THE CANDIDATES
Edwina Hart: Rosemary Butler, Christine Chapman, Jeff Cuthbert, Andrew Davies, Janice Gregory, Jane Hutt, Val Lloyd, Sandy Mewies, Gwenda Thomas
Carwyn Jones: Leighton Andrews, Lorraine Barrett, Jane Davidson, Alun Davies, Brian Gibbons, John Griffiths, Lesley Griffiths, Carl Sargeant
Huw Lewis: Irene James, Ann Jones, Lynne Neagle, Karen Sinclair, Joyce Watson
Source: Welsh Labour
She is also backed by Islwyn MP Don Touhig and Gower MP Martin Caton. She has also been nominated by nine AMs, which Mrs Hart's campaign said neither of the other two candidates could match.
Mr Murphy said he was supporting Mrs Hart after having "worked very well" with her during his almost five years in total as Welsh secretary.
"She had a very good relationship with government ministers," said Mr Murphy. "She is an excellent minister herself and she has a excellent background in the Labour movement."
Mr Jones's backers say they now have the support of more Labour assembly government ministers than the other candidates, with the latest the Social Justice Minster Brian Gibbons.
Aberavon AM Dr Gibbons said Mr Jones had "strong and deeply held Labour values". He follows Jane Davidson among fellow ministerial colleagues in backing him.
Dr Gibbons said Mr Jones could provide leadership under pressure and had the party "in his blood".
"That's why - from Aberavon to Amlwch - he is the person who can reach out to the membership right across Wales," he said.
Mr Jones's campaign team also said Labour's chief whip in the assembly, Carl Sargeant, had publicly endorsed him.
Mr Lewis's campaign, meanwhile, has been endorsed by the Co-operative Party, one of the affiliated bodies which will play a key role in the contest.
Mr Lewis's campaign said the Co-operative Party became the first Labour affiliate to announce its support for a candidate.
The Lewis camp also said there were messages of support from Cardiff South and Penarth MP Alun Michael and Karen Wilkie, deputy general secretary of the Co-operative Party.
Mr Lewis, whose campaign will be based at the Co-operative Party HQ in Cardiff, said: "This endorsement means a huge amount to me and is a real boost for the campaign.
"Over the weekend, I said it was time for the tittle-tattle to be replaced by the battle of ideas - there is no greater generator of ideas in Welsh politics than the Co-operative Party."