He has served as the National Executive Director of Peace Action, and was a 2008 Green Party candidate from Maryland for the United States House of Representatives in 2008.
The community organization was founded to combat the nuclear war fighting policies of the Reagan Administration.
From 1982–1987 Clark served as the Site and Program Manager with the Bucks County, Pennsylvania Association of Retarded Citizens, delivering services to the developmentally disabled.
Following his recent arrest for nonviolent protest, Clark defended himself pro se in U.S. District Court and was acquitted on all charges.
[2] Clark has also held the positions of field director of Public Citizen's Congress Watch, (2003–2006) and Project Coordinator, Chesapeake Climate Action Network, 2007.