Parti ouvrier français
The PSR was led by Édouard Vaillant, who sought to be the middle ground between moderate socialists (Jean Jaurès, Paul Brousse) and Marxists (Jules Guesde, Paul Lafargue). The PSR, however, later merged with the French Workers' Party (POF) to form the Socialist Party of France (PSdF). The PSdF was one of the two founding members of the French Section of the Workers' International (SFIO) in 1905.