I have been late to the party when it comes to last night's BBC Newsnight debate with the Labour leadership candidates, about which much has already been said, including on this blog.

So I'll stick to a few quick thoughts, ignoring questions of format and sticking instead to some of the comments made by candidates.

One of the most striking elements of the debate was the behaviour of Ed Miliband, who left no doubt at all that he is fighting, hard, to beat his own brother and win this contest. He said he wanted to be "prime minister" in his introduction and repeatedly attempted to interrupt David Miliband, on one occasion saying that Labour's fortunes were down to "more fundamental" issues than those which were being discussed. He seemed to have had a haircut, wore a smart pink tie, and peered straight into the camera, Nick Clegg-style, as much as he could.

David Miliband, perhaps the most consistently impressive candidate in the hustings, seemed a tiny bit subdued; perhaps he was simply given less airtime. But his pitch at the start, in which he outlined what is "real about me", was highly effective, as was his invoking the memory of Tony Crosland at the end.

The first question was about Gordon Brown, and it was striking that Ed Balls, supposedly the former prime minister's most loyal ally, was the most condemnatory, accusing him of having been proved "out of touch" in his encounter with Gillian Duffy. Both David Miliband, who critics assume was somehow disloyal to Brown, and Ed Miliband said it would be a "grave error" to blame Labour's election defeat on one moment of the campaign.

David Miliband said he didn't stand in 2007 "because I was not ready to be prime minister", but that "changing the leader" would not have been enough. The problems for the party, he said, went back to 2006, after which there wasn't a root-and-branch change of approach. He also pointedly hit out at "negative briefing".

Diane Abbott, for her part, tried to portray herself as "the people's candidate" as opposed to the "Westminster insider's candidate", but then emphasised that she had been in the Commons longer than anyone else on the platform, and knew Westminster well as a result.

Andy Burnham repeated his outsider pitch, and made a direct appeal to the unions, but the point of his candidacy may have still appeared a little unclear to the party if not the viewing public.

Depressingly, there was once again much discussion of immigration, with Burnham and Balls taking a tough line and the Milibands, while accepting it was "an issue on the doorstep", emphasising the "underlying issues" of housing and jobs. Abbott rightly said it would be a grave error to blame Labour's defeat on that issue.

But it was Ed Miliband who made the most controversial pitch, saying: "I don't see a contradiction between standing up for values and winning an election, because you can't have victory without values". Other candidates, including his brother David, may feel they too have values. But Ed is determined to portray himself as the "credible change candidate".

In this unpredictable leadership election, it remains to be seen whether he will overtake his authoritative brother.

Watch this space for my feature in this week's magazine on the background to David and Ed Miliband's fight for the leadership.