Three years later , JaurÃ s , Allemane and the possibilists founded the French Socialist Party while Guesde and Vaillant formed the Socialist Party of France . Three years later , JaurÃ s , Allemane and the possibilists founded the possibilist French Socialist Party , which supported participation in government , while Guesde and Vaillant formed the Socialist Party of France , which opposed such co-operation .