France's first socialist party, the Federation of the Socialist Workers of France (Fédération des travailleurs socialistes de France or FTSF), was founded in 1879. It was characterised as "possibilist" because it promoted gradual reforms.

fter the failure of the Paris commune (1871), the French socialism was beheaded. Its leaders were died or exiled. In 1879, during the Marseille Congress, workers' associations created the Federation of the Socialist Workers of France (Fédération des travailleurs socialistes de France or FTSF). However, three years later, Jules Guesde and Paul Lafargue (the son-in-law of Karl Marx) left the federation, which considered so moderate, and founded the French Workers' Party (Parti ouvrier français or POF). The FTSF, led by Paul Brousse, was defined as "possibilist" because it advocated gradual reforms, whereas the POF promoted Marxism.

In the same time, Edouard Vaillant and the heirs of Louis Auguste Blanqui founded the Central Revolutionary Committee (Comité révolutionnaire central or CRC), which represented the French revolutionary tradition.

In the 1880s, the Socialists knew their first electoral success, conquering some municipalities. Jean Allemane ans some FTSF members criticized the focus on electoral goals. In 1890, they created the Revolutionary Socialist Workers' Party (Parti ouvrier socialiste révolutionnaire or POSR). Their main objective was the "general strike". Besides, some deputies declared Socialist whereas they were not member of a party. They had moderate opinions.

In 1899, a debate opposed the Socialist groups about the participation of Alexandre Millerand in Pierre Waldeck-Rousseau's cabinet, which included the Marquis de Gallifet, best know for having directed the bloody repression during the Paris Commune. Furthemore, the participation in a "bourgeois government" sparked a controversy opposing Jules Guesde to Jean Jaurès. In 1902, Guesde and Vaillant founded the Socialist Party of France, while Jaurès, Allemane and the possibilists formed the French Socialist Party. In 1905, during the Globe Congress, under the pression of the Second International, the two groups merged in the French Section of the Workers' International.

It was hemmed in between the middle class liberals of the Radical Party and the revolutionary syndicalists who dominated the trade unions. Indeed, the General Confederation of Labour claimed its independance and the non-distinction between political and professional aims.