Several of France's leading socialist and republican figures of the early 20th century originally belonged to this current: Jean Jaurès (who went on to become the chief figure of the French socialist Party); René Viviani and Aristide Briand (both heads of government around the time of the first world war); Alexandre Millerand (head of state after the war).

These splinters meant that by 1935 the French Chamber of Deputies contained a diffuse array of about sixty parliamentarians situated between the SFIO and the PRRS, broadly sharing a tradition of non-Marxist reformist socialism and Radical republicanism.

After Renaudel's death in the spring of 1935 the PSDF leader Marcel Déat opened negotiations with the two Socialist Republican parties to coordinate the three groups' activities in parliament.

In the elections of 1936 the USR aspired to act as a midpoint between traditional Radicalism and orthodox Marxian socialism, expecting that the political crisis since 1933 had weakened voters' satisfaction with the traditional left parties: the Socialists for their rigid refusal to enter a reformist government that could mitigate the effects of the Great Depression; the Radical-Socialists for their ostensible lack of principle for having switched from an alliance with the Socialists to one with the conservatives midway through the legislature.

The SFIO now accepted participation in a coalition government dedicated to socio-economic reforms, while the PRRRS had now publicly positioned itself as a party of anti-fascism and thereby pledged to remain faithful to the electoral alliance of the left.

SIx of its members held cabinet rank during this period: Paul-Boncour, Frossard, de Monzie, Ramadier, Ramette, Patenotre and Pomaret.