Besson was a member of the Socialist Party from 1993 to 2007. He has been mayor of Donzère since 1995 and was the "député" for the Drôme between 1997 and 2007, when he did not stand for re-election. During his time as a Member of Parliament, Besson was a member of the National Commission for Defense and the Armed Forces from 1997 to 1998, the Financial and Economic Planning Commission from 1998 to 2002, the Commission of Inquiry on the Activity and Functioning of Commercial Courts, and the Commission of Inquiry on Superphénix and fast neutron reactors (both in 1998).