Commissioner Sizemore Jr. was first elected as a member of the Washtenaw County Board of Commissioners effective January 1, 2001.  For 2009 Commissioner Sizemore Jr. serves  as the Chair of the Board of Commissioners.

Commissioner Sizemore Jr. serves on the Community Action Board, Criminal Justice Collaborative, Drainage Board, Emergency Telephone District Board, Police Services Steering Committee, Public Safety and Justice Oversight Committee, Sheriff's Youth, Community and Special Projects Fund, and the Joint Willow Run Airport Zoning Board.