I thought I knew all about Ed Balls. But when I went to interview him for a piece in today's magazine, I was forced to think again.

Balls was one of the very few senior Labour figures -- along with Douglas Alexander and, to be fair, Ed Miliband -- who recognised the truth about David Cameron's leadership of the Tories: that it was not "centrist" but, in fact, a supremely skilful cover-up of what remained a conventional right-wing agenda on the areas that matter, such as fiscal policy.

He (rightly) attacked the Tories as right-wing while other New Labour figures awarded Cameron the tag of "moderniser".

Today, though he could be accused of lacking a coherent "vision" for Labour's future, he has already won the leadership contest when it comes to scrutinising the coalition government, with his articulate and forceful attacks on Tories and Lib Dems in equal measure.

Yes, he is hard, aggressive and combative. But his fearlessness and drive -- almost limitless -- are a lethal weapon against a fragile coalition that is crying out for strong opposition.

He is, as I say in today's piece, the only candidate willing to take on, for example, the dominant, Tory-dominated media in this country. Though he has allies in the right-wing and Murdoch press, one would hope he would be one of the very few politicians in Westminster unafraid of refusing to tailor his message, adapt his policies and award such media barons the disproportionate influence they do not deserve.

I can think of only Kenneth Clarke and Charles Kennedy who, if they were in positions of power, would defy Rupert Murdoch. I like to think Balls would do the same.

Balls is a divisive figure, without question. But he is supposedly the "Marmite" candidate you either love or hate. On this I disagree. He -- and his candidacy -- are a complicated mix. He will probably not win: the crown will almost certainly go to one of the Miliband brothers. But that he has earned his place as a very serious contender is no longer in doubt.

In my piece, I make a small confession, saying I have at times been wary of him. Well, here is another confession (forgive the self-indulgence): I am something of an Ed Balls convert.

And no, that is not an endorsement. But it is an appeal for everyone to consider all the candidates with an open mind.