In 1931, Doriot was elected mayor of Saint Denis. Around this time, he came to advocate a Popular Front alliance between the Communists and other French socialist parties with whom Doriot sympathized on a number of issues. Although this would soon become official Communist Party policy, at the time it was seen as heretical and Doriot was expelled from the Communist Party in 1934. Still a member of the Chamber of Deputies, Doriot struck back at the Communists who had renounced him: now bitter towards the Comintern, his views turned to embrace the French nation, evolving into a 'national' socialism—as opposed to the socialism of the Third International. By now embodying fascist more than socialist ideals, Doriot founded the ultra-nationalistParti Populaire Français in 1936. Doriot and his supporters were vocal advocates of France becoming organized along the lines of Fascist Italy and Nazi Germany and were bitter opponents of Socialist Premier Léon Blum and his Popular Front coalition.
Collaboration
When France went to war with Germany in 1939, Doriot became a staunch pro-German and supported Germany's occupation of northern France in 1940. Doriot resided in collaborationist Vichy France for a time, but he eventually found that it was not nearly as Fascist as he had hoped it would be and moved to occupied Paris, where he espoused pro-German and anti-communist propaganda on Radio Paris. In 1941, he and fellow fascist collaborator Marcel Déat founded the Légion des Volontaires Français, a French unit of the Wehrmacht. Doriot fought with the LVF and saw active duty on the Eastern Front when Germany invaded the Soviet Union in June 1941 and was awarded the Iron Cross in 1943. In his absence leadership of the PPF officially passed to a directorate, although real power came to lie with Maurice-Yvan Sicard. In December 1944, Doriot travelled to Germany and made contact with the former members of the Vichy regime and other collaborators who had gathered together in the Sigmaringen enclave. Doriot's PPF struggled to assume a leadership role within the French expatriate community, basing itself in Mainau and setting up its own radio station, Radio-Patrie, at Bad Mergentheim and publishing its own paper Le Petit Parisien. The PPF was also involved in conducting intelligence and sabotage activities by supplying some volunteers whom the Germans dropped by parachute into liberated France. He was killed on 22 February 1945 while traveling from Mainau to Sigmaringen when his car was strafed by Allied fighter planes. He was buried in Mengen.