By Stephen Sackur BBC Europe correspondent

Peter Mandelson established his political reputation by taking a failed political institution and reinventing it as a modern, dynamic agent of change.

But that was the British Labour Party in the early 1990s.

Team player? Mandelson is an enthusiastic European

What of the enlarged European Commission in the first decade of our new century?

Many political observers and commission veterans here in Brussels are wondering whether Mr Mandelson's mastery of the darker political arts will help revitalise or further diminish the reputation of the EU's complex executive body.

"He's not exactly a team player, is he?" harrumphed one commission official when news of Mandy's nomination became official.

Another pointed to Mr Mandelson's political track record in Britain (including two painful resignations) and wondered aloud whether this was the right man for a commission desperate to lose its reputation for maladministration.

Political clout

In the end, though, Mr Mandelson brings to Brussels two attributes which matter.

First, he is a man of undoubted political talent who has an enthusiasm for Europe and an ability to deal with complex political challenges. (And goodness knows being an effective commissioner is a complex political challenge.)

He said he would be happy to be in charge of paperclips if necessary, but in reality he wants one of the big economic portfolios

Second, he brings with him substantial political clout - Brussels-based politicos know that Mr Mandelson is extraordinarily close to UK Prime Minister Tony Blair.

That gives him important leverage in a town which sometimes seems over-stuffed with European political veterans who have been put out to grass and who seek nothing more than a quiet life.

And in the end, of course, Mr Blair did not present the new president-elect of the commission, Jose Manuel Barroso, with a choice.

Rather than offering a couple of names, Mr Blair made plain his desire to see the UK seat on the commission occupied by his close ally.

There was, say diplomats, a "positive response" from Mr Barroso - and it is indeed true that the former Portuguese prime minister has had several amicable chats with the well-connected Mr Mandelson in the past - but there is little doubt that the commission chief would have been delighted if Mr Blair had come up with a female nominee.

Arm-wrestling

Mr Barroso wants eight of his 24 new commissioners to be women - so far, he has just three in the frame.

Mr Mandelson will not take up his new post until November. Before then, he has to be given a specific portfolio.

He said he would be happy to be in charge of paperclips if necessary, but in reality, he wants one of the big economic portfolios which lie at the heart of the commission's work.

That means a period of political arm-wrestling with the French and the Germans.

And then there is the small matter of getting the new commission approved by the European Parliament.

Serious doubts about Mr Mandelson's merits may be expressed by MEPs, but no-one really believes his presence will jeopardise formal ratification of the new team.

So three months or so from now, Mr Mandelson will take up another daunting political challenge: to make Europe more attractive to the British public and help making the ailing commission a more dynamic agent of European renewal.