Andrew Grice: Cain versus Abel, this leadership contest has come alive at long last

Inside Politics

I once shared a taxi with the twentysomething Miliband brothers in a rain-swept Blackpool during Labour's annual conference.

Bizarrely, they knew who I was but I didn't know which one was David and which one Ed. To my discomfort, the traffic didn't move. I tried not to let my ignorance show – and failed.

With one of them set to be crowned Labour leader four weeks today, we can certainly tell them apart now. In the past week, the relationship between the two sons of the Marxist historian Ralph Miliband has probably changed forever. They may still speak of their "love" for each other but this weekend there is little love lost between them as they vie for the crown.

Perhaps it was always a bit naïve for the brothers to think they could stand against each other without harming their relationship. Despite David Cameron's brilliant gibe about the Labour race looking like a "Star Trek convention", the Milibands are different people with different views. In a close contest – and it could be a photo-finish between them – the relationship was bound to be stretched to breaking point.

Unlike The Godfather, now it's personal as well as business. The great irony is that, at the start of the race, all five Labour runners agreed on the need to move on from the psychodrama of the Blair-Brown years. Now the danger for the party is that it replaces one psychodrama with another. First, the endless, debilitating struggle between the modernising blood brothers. Gordon Brown and Tony Blair were described as Peter Mandelson's "son number one and son number two", although he preferred to call the three of them a "band of brothers". Now we could have a Cain and Abel fight between two real brothers. Why? For the most part, Labour's leadership election has been conducted in a civil and coded way. It is a million miles from the first Labour election I covered – a bitter left-right battle for the deputy leadership between Tony Benn and Denis Healey.

Labour's ideological differences have narrowed since 1981. But the Miliband brothers diverged this week over how the party should respond to its election defeat. Ed is spitting blood, claiming that David is portraying him as a latter-day Bennite who wants to target Labour's core working-class vote rather than the middle classes central to its three victories under Mr Blair.

David Miliband's camp, which won the backing of 1,000 Labour councillors yesterday, believes his brother is fighting a carefully calculated campaign to win the second preference votes of those candidates most likely to be eliminated first – Diane Abbott and Andy Burnham. But they argue that his tacking to the left could not be washed away after the event; leadership elections define leaders in the public's and the media's minds.

So David's followers fear Ed Miliband would lead Labour into a cul-de-sac. Likening him to Neil Kinnock, they claim Mr Brown described Ed Miliband as a "preacher" who tells people what they want to hear. Mr Brown is remaining neutral but is said to want Ed Miliband to win, seeing him as offering the best hope of defeating his brother.

Ed Miliband rejects the charge that he would take Labour back to its "comfort zone". He argues the party can no longer take its natural supporters for granted and that it is time to move on from the "New Labour comfort zone".

Their differences becomes starker in their responses to my questions to all five candidates, published in The Independent today. Ed pronounces New Labour dead, while David insists it is very much alive. Ed hints at higher taxes to minimise spending cuts.

Ed Balls, who is having a good war fighting the Coalition Government, reveals his understandable frustration at the media turning Labour's contest into a two-horse race; he fears a self-fulfilling prophecy. Yesterday he showed he is not about to throw in the towel by revealing he opposed as "too fast" Alistair Darling's decision to halve the deficit over four years, hinting that the then-Chancellor even overruled Mr Brown. "I thought it would be very difficult for them to command wider market and public support because it could put growth and jobs at risks and it could put public services at risk," Mr Balls told the BBC.

At least a rather soporific contest has now come alive. The brothers' war of the comfort zones may sound esoteric but goes to the heart of the debate about Labour's future. David M's allies believe it is a turning point, expressing optimism that Labour will not risk sending a signal it is not interested in affluent voters by choosing Ed M.

David Miliband is no Blair clone but, inevitably, is struggling to rip off the Blairite label that is stuck to him. It will damage him because the party does want to move on.

Publication of Mr Blair's memoirs next Wednesday, the very day that Labour's ballot papers go out, will hardly help David Miliband.

Mr Blair is also keeping out of the Labour race but it is no secret that he would want David to win.

However, some close Blair allies fear that, in defeat, Labour will turn to a "therapist" rather than a strong leader who would challenge his own party in order to win power. That would mean Ed, not David.