Mark Stuart: Two brothers in arms launch a family battle to put Labour back in business

This will primarily be a contest which pits David Miliband against his younger brother Ed. But who will triumph now that these brothers have taken up arms against each other?

It came as no surprise that elder brother David was first out of the starting blocks; the former Foreign Secretary has had his campaign manager in place since January.

By declaring his candidacy early, David's aim was to create a mood of unstoppable momentum, shown when he received the backing of key Blairites within the party, including Alan Johnson, Caroline Flint and Lord (Charlie) Falconer. But by appearing to jump the gun, David misjudged the mood of the Labour Party.

Most MPs and members didn't want a rushed contest, and now Labour's ruling body has decreed that the whole business will drag on until September.

It's akin to 1992 when the departing leader, Neil Kinnock favoured a swift contest, but the party at large wanted to slow the process down in orderto reflect properly on their election defeat.

Despite being the bookmakers' favourite to seize the Labour crown, David Miliband hardly set his candidacy alight when he appeared outside the House of Commons flanked by barely a dozen MPs; it resembled more a motley crew than an unstoppable phalanx of leading former frontbenchers.

David will of course, not have wished to exhaust his number of backers in one go. Even so, the most noticeable feature of Labour's election defeat was that it severely depleted the number of Blairite MPs in the House of Commons, so if David is to win, he needs to be able to appeal beyond his natural support base on the right of the party.

While there is little doubt that David has the necessary intellect for the top job, he would be deluding himself if he thinks he has the same

charm as his mentor, Tony Blair.

Rather, the indelible impression is of a school-swot-turned-Labour-Party-anorak – very good when it comes to crafting policy behind-the-scenes, but lacking the human touch required of a modern leader in the television age.

Enter Ed Miliband, who at least has the merit of possessing a modicum more personality than his older brother, having charmed the online users of Mumsnet in the run-up to the election campaign.

Ed has also received high-profile backing in the shape of Derek Simpson, joint general-secretary of the powerful Unite union. However, Simpson and his fellow union barons no longer wield the same power as they used to, thanks to John Smith's introduction of One Member, One Vote in 1993: millions of ordinary trade union members will be

allowed to make up their own minds in one of the biggest exercises of democracy short of a general election.

In order to win, budding candidates must have some appeal with trade unionists, something that is up for grabs now that union-friendly Jon Cruddas has decided not to stand. Much depends on who Cruddas backs.

If press rumours are correct, and Cruddas has already done a deal with David Miliband, this could form an unstoppable "dream ticket" which would probably propel the elder of the Miliband siblings to victory.

Although Ed Miliband is the only other serious contender, his chances of winning may be thwarted by the decision of his namesake, Ed Balls, to stand for the leadership.

Both Eds are likely to attract support from the centre and left of the

Party. Indeed, conspiracy theorists suggest that Ed Miliband is merely standing to peel away votes from Balls in order to help his elder brother. I don't believe those claims for a minute. Ed genuinely wants to win this contest, even if it means defeating David.

Moreover, there are clear signs already that Ed is in a better position than his older brother to distance himself from New Labour's unpopular policies. In particular, the Doncaster North MP's condemnation of the war in Iraq is a shrewd move: Ed wasn't in Parliament at the time (an advantage he shares with Ed Balls), unlike his brother, David, who voted in favour of military action. For all David's efforts to distance himself from his Blairite credentials in recent interviews – claiming that he is more interested in "Next Labour" than "New Labour" – he will find it very hard to represent the future.

By way of contrast, brother Ed realises that his party became stuck in what he terms the "old orthodoxies", particularly when it came

to losing the trust of people on immigration. His recipe is radical change, offering a fresh agenda that seeks root and branch reform of the welfare state to make it fit for the 21st century.

So, Ed Miliband is not merely a clone of his older brother. He has his own set of values, and is willing to engage in a major re-think of Labour policy. I believe that he represents Labour's best hope of returning to government.