The party was formed in 1972 by a split from the Republican, Radical, and Radical-Socialist Party, once the dominant party of the French Left. It was founded by Radicals who opposed Jean-Jacques Servan-Schreiber's centrist direction and chose to join the Union of the Left and agreed to the Common Programme signed by the Socialist Party (PS) and the French Communist Party (PCF). At that time, the party was known as the Movement of the Radical Socialist Left (, MGRS), then as the Movement of Radicals of the Left (, MRG) after 1973.