As the EU's chief negotiator, he has often defended the indefensible.

ECONOMIST: Trading places

Olli Rehn, the EU's current enlargement chief, likens the EU accession process to a journey that matters as much as the destination.

ECONOMIST: Enlargement enriches old as well as new members

As the chief policeman for unfair state aid in the 27-country EU, he will also play a decisive role in the overhaul of troubled Spanish banks and the setting up of a new, powerful banking supervisor for the euro zone.

WSJ: Economics Guru Jumps