General Motors is famous on Madison Avenue for being loyal to the agencies on its roster. Campbell-Ewald, for example, has created campaigns for the Chevrolet brand since 1914. "The wheel wasn't invented then," one agency executive who works for G.M. said facetiously.1958, OK. 1930s, uh, maybe? 1914? Holy shit! Same company? Campbell-Ewald hasn't missed a beat in 92 years? Come on! Status quo, people! It's killing you! Fuck it up! Get rid of whatever you are doing and whoever you are dealing with and do the opposite! Crap! We're so upset about this that now we're going to go snuggle with our wife.
As for the other main marques, Leo Burnett and its predecessor agencies have produced campaigns for Pontiac since 1935 and Cadillac since 1936. Buick has been handled by McCann Erickson since 1958.