General Motors is consolidating all advertising work for the Chevrolet brand under the McCann unit Commonwealth, which means the agency now handles all of Chevrolet. On the losing end of the deal is now former-incumbent Leo Burnett. Commonwealth was formed in 2012 under GM's then CMO Joel Ewanick as a joint venture between Omnicom's Goodby, Silverstein & Partners, and Interpublic's McCann Erickson Worldwide.