Agency roster: Interpublic Group of Cos.' Campbell-Ewald, Lowe and McCann-Erickson Worldwide and GM Mediaworks. Publicis Groupe's D'Arcy Masius Benton & Bowles , GM Planworks and Leo Burnett USA. Omnicom Group's Goodby, Silverstein & Partners. Modernista!
Power play: Mr. Middlebrook, 61, stopped a market share slide with big incentives, swanky sport-utilities, improved vehicle quality and splashy ads. He also streamlined GM's brand management and product development processes, which had been hindrances.
Downside: He needs to wean buyers off incentives and build strong brands that sell with lesser deals.