WHO could replace Ed Miliband as Labour leader? Here are some of the potential runners and riders.
Fourth out of the five in the last leadership contest in 2010, the 45-year-old MP for Leigh is the bookies’ favourite to win the next one and has strong support among trade unions.
Holding the key health brief in government and opposition for most of the last six years has helped make the 45-year-old a darling of the Labour grassroots.
The passionate Everton fan’s credentials were also enhanced by his instrumental role in having the inquiry into the Hillsborough disaster reopened as a cabinet minister in 2009.
But critics fear he would be vulnerable to attack because of being health secretary at the time of the Mid Staffs excess deaths scandal.
Labour has never elected a female leader - Margaret Beckett and Harriet Harman have both stepped up temporarily from the deputy role - and Ms Cooper has long been tipped to be the first.
One stumbling block to a tilt at the top job - the leadership ambitions of her husband Ed Balls - has been dramatically removed by the voters of Morley and Outwood who voted him out of the Commons.
The shadow home secretary has built a reputation as a safe pair of hands in a succession of ministerial and opposition jobs, rarely if ever finding herself embroiled in controversy.
But, like with Mr Burnham, she may be considered too much a part of the old guard by a party seeking a new start.
A rapid rise to the shadow cabinet makes it easy to forget the he has only been an MP since 2010 so could certainly be presented as a fresh face.
The sharp-suited, smooth-talking former employment lawyer has made a mark as shadow business secretary and has previously declined to rule out a leadership bid.
In 2011 the sometime DJ who ridicules the “British Obama” epithet attached to him as the man most likely to become Britain’s first ethnic minority party leader, said it would be “arrogant” to claim to be the best candidate but raised the prospect of a vacancy around now.
The shadow health minister has been touted as a potential torch bearer for the Blairite right of the party, recently burnishing her claim to that market-friendly mantle with a bold declaration that “what works” should be the priority for the NHS.
By striking such a distinct tone from Mr Burnham - to whom she was number two in the shadow health team - she was considered by Westminster watchers to have signalled her ambition.
A former special adviser to Harriet Harman and then health secretary Patricia Hewitt - whose Commons seat in Leicester she inherited - she has a background in health bodies and charities.
Consistently tipped as the dark horse in the potential field of replacements for Mr Miliband, the Barnsley Central MP certainly appeals to those seeking a move away from career politicians.
In 2011 he ended a 15-year career as a Para, including tours in Afghanistan, Iraq and Kosovo and as a special forces support group company commander, for a safe seat in the Commons - the first to make such a switch since the Second World War.
The married father-of-three was quickly handed shadow ministerial roles in culture and justice.
He swerved the question of whether he would throw his hat in the ring after increasing his majority in Barnsley Central in the General Election.
The veteran ex-cabinet minister’s name will inevitably crop up in speculation about the possible line-up of candidates despite insisting recently that he had never stood for the leadership of his party and “regardless of the circumstances never will”.
His stature in the party was in evidence last year when he was said to have been approached by senior figures in the party to consider taking on the role amid a bout of internal wobbles over Mr Miliband’s performance.
A former postman and senior union official whose memoir of a poverty-ravaged childhood in London slums proved an instant hit, he was Mr Miliband’s first choice as shadow chancellor before quitting for personal reasons.
john McDonnell/Diane Abbott
One or both could emerge as a challenger from the left of the party.
Mr McDonnell, chair of the Socialist Campaign Group, has been a consistent critic of party leaderships and sought to challenge the unopposed handover from Tony Blair to Gordon Brown but failed to secure sufficient backers.
In 2010 he abandoned his leadership bid to allow a better run for Ms Abbott, the outspoken veteran who eventually came last in the contest won by Mr Miliband.