PSOE. Partido Socialista Obrero Español. Spanish Socialist Workers' Party. Current leader (2008) José Luis Rodríguez Zapatero. The Spanish Socialist Workers' Party is a social-democratic party and ruling party in Spain since the general election of March 14, 2004 until 9th Martch 2008. It forms part of the Party of European Socialists and is a member of the Socialist International