Following the Dreyfus Affair, Pierre Waldeck-Rousseau composed in June 1899 a "Republican Defense Cabinet" (gouvernement de défense républicaine), which was supported by a parliamentary majority composed of Radicals, Radicals-Socialists and Socialists. This majority decided to ally themselves in view of the 1902 elections, which they won. The Bloc des gauches was thus represented at the Chamber of Deputies by four parliamentary groups: the Democratic Alliance (Alliance démocratique, AD), the Radical Left and the Radical-Socialists and the Socialists. Under Emile Combes's leadership, the new government enacted an anti-clerical policy, passing the 1905 French law on the Separation of the Churches and the State, and opposed itself to the nationalist movement.
"Opportunist Republicans" who opposed the alliance with the Radicals, the Radicals-Socialists and the Socialists, and, for some of them, the defense of the Jewish officer Alfred Dreyfus, founded in November 1903 the Republican Federation (Fédération républicaine), which represented the Republican bourgeoisie, closely connected to business circles and opposed to social reform.
Following the International Socialist Congress of Amsterdam in 1904, the Socialists were called by Jules Guesde's Socialist Party of France (Parti socialiste de France) to quit the government. The Socialist ministers thereafter withdrew themselves from the Republican Coalition, which dissolution was completed in October 1906 with the coming of Georges Clemenceau to power.