 He joined the Socialist Party (PS) after the 1971 Epinay Congress during which François Mitterrand took the party leadership.Ayrault was affiliated to Jean Poperen's faction, one of the left-wing groups in the party.Elected in 1976 to the General Council of Loire-Atlantique "département", he subsequently became Mayor of Saint-Herblain, located in the western suburbs of Nantes, in 1977.