McKenna served as Washington attorney general from 2005 to 2013. He was first elected to the position in 2004. He won re-election in 2008. for more information on McKenna's election participation and results.

In November 1995, McKenna was elected as one of the 13 members of the Metropolitan King County Council, representing the cities of Bellevue, Mercer Island, Kirkland, Newcastle, and Renton. Within this role, he wrote laws specializing in budget, land use, and transportation. He was re-elected without opposition to the position in 1999 and 2003.