South Shields MP David Miliband took his Labour leadership bid on the road as he seeks to gain an early advantage in the race to succeed Gordon Brown.
The former foreign secretary was the first to announce he was running for the job, declaring his candidacy on Wednesday night within 24 hours of Mr Brown's resignation.
He set out on a "conversation" tour of the UK yesterday to find out from voters why they turned away from Labour in their millions in last Thursday's general election.
Meanwhile, former Cabinet Minister Ed Balls was yesterday night sounding out colleagues over a possible bid for the Labour Party leadership.
Mr Balls said he would decide "in due course" whether to stand against the only currently declared candidate David Miliband.
Former foreign secretary Mr Miliband said he hoped as many candidates as possible would stand and indicated his rivals could include his "immensely talented" younger brother Ed.
Mr Balls said the Labour Party wanted a "proper debate" about the lessons which needed to be learned after the election.
The former schools secretary said: "I'm obviously talking to people but I don't want to jump to any quick conclusions."
Mr Balls, a close ally of former Prime Minister Gordon Brown, faced a tough fight to win his Morley and Outwood seat in West Yorkshire with a majority of just over 1,000 at last week's general election.
He told BBC News: "I think the pretty strong message from the Parliamentary Labour Party was they wanted to make sure that we talk about what's happened in the election last week in a constituency like mine, where it was closely won, but there are some real issues for us to look at.
"There's got to be a proper debate, people want a proper debate and I'm going to take that very seriously.
"I'm talking to people in the parliamentary party and in the wider country too and I will decide in due course."
There is fevered anticipation at Westminster that David Miliband's brother - Ed Miliband - as well as Andy Burnham, are on the verge of announcing their own bids too. Another challenge could come from popular backbencher Jon Cruddas, who on Wednesday night addressed Labour activists in Westminster as he weighed his options.
In a forceful intervention in the debate about Labour's future, Mr Cruddas urged the party to look to its record in office to understand why it had alienated some of its core supporters. He said Labour should be "under no illusion" about the extent of its defeat, its 29% vote share last Thursday representing its worst performance since the party's 1983 nadir under Michael Foot.
Mr Miliband said the decision of the Liberal Democrats to join a Conservative government was "a momentous one".