The French Socialist Party (French: Parti socialiste français, PSF) was founded in 1902. It came from the merger of the "possibilist" Federation of the Socialist Workers of France (FTSF), Jean Allemane's Revolutionary Socialist Workers' Party (POSR) and some independent socialist politicians like Jean Jaurès. Jaurès became the party leader.
Unlike the Socialist Party of France led by Jules Guesde, it supported the principle of the alliance with the non-Socialist left in the Bloc des gauches. Finally, in 1905, under pressure from the Second International, the two parties merged into the French Section of the Workers' International.
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French Socialist Party (1902) Wikipedia(Text) CC BY-SA