The 2006 United States Senate election in Pennsylvania was held on November 7, 2006. Incumbent Republican Rick Santorum ran for re-election to a third term, but was defeated by Democrat Bob Casey, Jr., the son of former Pennsylvania governor Bob Casey Sr. Casey was elected to serve between January 3, 2007 and January 3, 2013. As of 2022, this was the last time the following counties have voted Democratic in a Senate election: Greene, Washington, Westmoreland, Somerset, Lawrence, Mercer, Armstrong, Indiana, Cambria, Warren, Forest, Elk, Clearfield, Clinton, Schuylkill, Columbia, and Carbon.