 After joining the Socialist Party in 1976, he was successively elected municipal councillor of Massy (1983), General Council of Essonne (1985) and Senator of the same department (1986, reelected in 1995 and then 2004).He also served as Minister for Vocational Education between 2000 and 2002, under Minister of National Education Jack Lang, in the cohabitation government of Lionel Jospin.He was part of the left wing of the Socialist Party until the Reims Congress of 2008, at the outcome of which he left that party to found the Left Party with Marc Dolez, a member of the National Assembly.