Tony Blair's ex-communications chief Alastair Campbell says he will back Alan Johnson as deputy Labour leader.
He told the BBC his biggest consideration was keeping Labour in power, and that he believed Mr Johnson would help the party achieve that.
"You know what I'm thinking about is who will best complement Gordon, who's going to be leader," Mr Campbell said.
Mr Johnson faces Hazel Blears, Peter Hain, Hilary Benn, Harriet Harman and backbencher Jon Cruddas in the race.
Mr Campbell told BBC Five Live: "I'm really thinking about the best kind of combination that's going to help the Labour Party stay in power.
"I think that if you get Gordon, with his strengths and experience, I think Alan's got a very attractive personality and has also got a real understanding of the Labour Party and Labour politics."
Mr Johnson is one of six candidates in the running
He said: "You then throw in the David Milibands and all the rest of it, who are going to become the young kind of intellectual driving forces and I think we'll be in a very very strong position come the next election."
He said he did not believe the deputy leader had to be a woman.
"I think the deputy has got to be the person who best complements Gordon Brown's skills as leader," he said.
Mr Benn launched a bid on Friday to replace John Prescott, saying the party should be "unapologetic about our values" and pledging a "more straightforward kind of politics" if he became deputy leader.
Mr Cruddas' campaign received a boost earlier when London mayor Ken Livingstone backed him.
Mr Livingstone praised Mr Cruddas' "tenacity" in campaigning against the BNP in his Dagenham constituency, in East London, and said he had made a "thoughtful" contribution to the debate on the future of the party.
Mr Benn, who launched his campaign earlier at Toynbee Hall, in East London, was the last of the deputy contenders to gain the required 45 nominations to get on to the ballot paper, Mr Benn's campaign team said he had strong support within the party.
On Friday, the Leeds Central MP told his launch audience, which included his father Tony: "The first task of the deputy leader ... will be to put Labour at the centre of a new and more straightforward kind of politics."
His other aims would be to empower communities and encourage the party to be "bolder" about the society Labour wanted to create.
He emphasised that Labour had to "talk straightforwardly about the future we want" and urged members to vote for the next deputy leader.
Hilary Benn urged Labour members to have their say
"No politician can create this society alone, as real leadership means having the humility to listen as well as the courage to act," he said.
"The corridors of power belong to the British people, and making sure your voice is heard along them is why I am standing to be deputy leader."
The six contenders will take part in a series of hustings around the UK, starting on Sunday in Coventry.
Voting forms will go out to Labour Party members, MEPs and trade unionists from 1 June, with the ballot due to close on Friday, 22 June.