Ed Miliband may stand against his elder brother, David, in the Labour leadership election that will be sparked by Gordon Brown's sudden decision last night that he is to stand down this autumn.
David Miliband, the Foreign Secretary, and Ed Balls, the Schools Secretary, had been seen as the two front-runners to succeed Mr Brown. But friends of Ed Miliband, the Energy and Climate Change Secretary, made clear last night that he is considering whether to throw his hat into the ring.
Close allies said he wanted the Labour Party to have "the widest possible choice" to ensure it used the contest to have a wide-ranging debate on ideas. They said there was no need for him to make an early decision and that his focus was on the talks with the Liberal Democrats on a possible Lib-Lab coalition. He was involved in informal discussions with the Liberal Democrats over the weekend.
A "battle of the brothers" between the two sons of the late Marxist academic Ralph Miliband would add another twist to what already promises to be a fascinating contest. Supporters of David believe it is his "turn" and argue that Ed lacks the experience of a senior post such as the Foreign Office, saying his time will come.
However, Ed has grown in stature in his climate change brief and attracted growing support on the Labour back benches. His backers argue that David lost support by failing to strike against Mr Brown during the three failed coups against him before the general election. "He has missed his chance," one said.
Labour's new leader will be chosen by the time of the party's annual conference in Manchester in September. The electoral college gives a third of the votes each to Labour MPs, the trade unions and party members. As potential rivals eyed each other when the Cabinet met in Downing Street last night, Brown aides said they did not want candidates to declare immediately or to start campaigning while the country remained in limbo after last week's election resulted in a hung parliament. But such hopes looked forlorn as friends of some candidates spoke openly about their intention to run.
One government insider said: "The next leader will be called Ed or Miliband. No, let me correct that. He will be called Miliband or Miliband."
Yvette Cooper, the Work and Pensions Secretary, who is married to Mr Balls, might have entered the leadership race if he had lost his Morley and Outwood seat last week, but he survived and she will not stand against him. That will put pressure on Harriet Harman, Labour's deputy leader, to run for the top job so that there is a female contender. But friends signalled that she was unlikely to stand, on the grounds that the torch should pass to a younger generation.
Mr Brown will not endorse any candidate. Nor will Lord Mandelson, the Business Secretary and unofficial deputy Prime Minister.
A Labour spokesman said: "Gordon Brown has always felt the most important priorities for the country are securing the recovery and changing our politics for good. Gordon Brown's words today were the mark of a man who has always put his country first. The Labour Party's National Executive Committee will meet in the coming days to determine the procedures for a leadership election."
To be a candidate when there is a vacancy requires nomination of 12.5 per cent of the Parliamentary Labour Party (PLP) – 33 MPs at present. There is a higher hurdle if a candidate wants to mount a challenge against the leader, when he or she requires nominations from 20 per cent of the PLP.
Candidates can be nominated by MPs, MEPs, affiliated organisations and constituency parties, and must confirm their willingness to stand two weeks before voting is triggered.
At the last contested election of a Labour leader, in 1994, some 700,000 people were entitled to cast a ballot, but their votes were not all worth the same. Because the electoral college is divided into three sections, the vote of an individual MP is worth more than that of a grassroots activist or union member.
The first section is made up of MPs and MEPs; the second of individual members of the Labour Party; and the third of members of affiliated organisations, including 15 trade unions, the Co-operative Party, the Fabian Society, Labour Students and other groups including ethnic minority, gay and disabled-supporter associations.
Trade union members who have opted out of paying a political levy are not entitled to vote on the leadership. Union leaders no longer cast a block vote for their unions but union members vote on a "one member, one vote" basis.
Voting takes place under the alternative vote system, in which candidates are numbered in order of preference. If one candidate receives more than half of first preferences, after ballots have been weighted in accordance with the electoral college system, he or she becomes leader.
If no candidate crosses this threshold, the individual with the fewest first preferences is eliminated and his or her second preferences are redistributed among the others. The process of elimination and redistribution continues until one of the hopefuls has secured more than 50 per cent support.
How will the Labour leadership election work?
As Gordon Brown has announced he is stepping down, there is no need for any formal challenge of leadership. Instead, prospective leadership candidates must secure the support of at least 12.5 per cent of the Labour Party's sitting MPs, which equates to 33 of the 258 seats Labour won on 6 May.
Those who are successful would then write to Labour's general secretary, currently Ray Collins, formally announcing their plans to run for the leadership. A special Labour Party conference will then be called to select a new leader by ballot before the autumn conference, currently scheduled for 26-30 September. The leadership contest will be decided by a straight majority in an "electoral college" system, in which the power is divided equally between Labour MPs, ordinary party members, and the membership of affiliated trade unions.
Each member of these groups gets one vote and ranks candidates in order of preference. The results of those who come top are calculated as a percentage of the total votes cast in that section of the college (i.e. expressed as a percentage of 33.3 per cent). The three sections' percentage results are then added together, and any candidate with a majority is declared the next leader. If no one achieves this in the first round, the candidate in last place is removed, and second preferences are redistributed until one candidate passes the 50 per cent mark.
Contendors for the Labour leadership
Alan Johnson, 59, Home Secretary
May decide not to run and has said he does not see himself as Prime Minister. But some allies say he would be the right man to head a coalition with the Liberal Democrats as he backs PR. Liked across party but missed chance to land deputy leader's post in 2007.
Appeal to the Lib Dems ****
Jon Cruddas, 48, Backbench MP for Dagenham and Rainham
Darling of grassroots who had strong showing in deputy leadership election in 2007, when he won most first-preference votes. Lacks ministerial experience but would enjoy support among unions and party members. Outward-looking and open to links with Liberal Democrats.
Appeal to the Lib Dems ***
David Miliband, 44, Foreign Secretary
Former Downing Street head of policy under Tony Blair. Will be seen as standard-bearer of Blairites but will position himself as slightly to the left of Blair to broaden appeal to his party. Keen on constitutional reform and therefore has his fans amongst the Liberal Democrats.
Appeal to the Lib Dems ****
Ed Miliband, 40, Energy and Climate Change Secretary
Younger brother of David and seen as to the left of him. Considering whether to stand against him or run his campaign. Being urged to run by admirers who believe he would appeal to a wider section of the Labour Party – and the voters. Liked by Liberal Democrats.
Appeal to the Lib Dems ****
Ed Balls, 43, Schools Secretary
Gordon Brown's closest political ally and former chief economic adviser at the Treasury. Would be seen as a Brownite candidate and to the left of his main rivals. Would enjoy strong support from trade unions. Wife Yvette Cooper, the Work and Pensions Secretary, may have run if he had lost his Commons seat last week.
Appeal to the Lib Dems **
Harriet Harman, 59, Leader of the Commons
Support in the party shown when she defeated Alan Johnson for deputy leadership in 2007. Will face pressure to stand again to ensure Labour has option of choosing a woman, but she appeared to rule herself out last night, saying she wanted to stay on as deputy and as a result could not run for leader or back anyone else.
Appeal to the Lib Dems **