Wikipedia
Tripartisme was the mode of government in France from 1944 to 1947, when the country was ruled by a three-party alliance of communists, socialists and Christian democrats, represented by the French Communist Party (PCF), the French Section of the Workers' International (SFIO) and the Popular Republican Movement (MRP), respectively. The official charter of tripartisme was signed on 23 January 1946, following the resignation of Charles de Gaulle, who opposed the draft of the constitution. The draft envisioned a parliamentary system, whereas de Gaulle favored a presidential system.
The traditional political class, which had included all the right-wing parties plus the Radical-Socialist Party that symbolized the Third Republic (1871–1940), was completely discredited by 1944. The reasons for this perceived lack of legitimacy included in the first instance the Collaborationism of several of these actors, as well as the failure in the 1930s to put an end to the economic crisis that had characterized the years of the Great Depression. Thus the Democratic Republican Alliance, the main center-right party after the First World War, had opted for Collaborationism, an option endorsed by its leader Pierre-Étienne Flandin plus other members like Joseph Barthélémy.
Furthermore, the political class was considered jointly responsible for the collapse in 1940 of the Third Republic following the disastrous Battle of France, which the historian Marc Bloch later described as the "strange defeat" (l'étrange défaite). In this way Gaullism and Communism emerged as the most popular political forces in the country.
However, Charles de Gaulle, who favored a presidential system, quit the government in 1946 and henceforth remained in the opposition until his triumphal return during the May 1958 crisis. For their part, the MRP, SFIO and PCF each achieved somewhere between 20% and 30% of the votes, with approximately 150 deputies each between September 1944 and May 1947. Afterwards, the PCF and de Gaulle's Rally of the French People (RPF) became France's main parties; however, both remained in opposition, because on their own they could not muster the absolute majority needed to form a government, and an alliance between them was inconceivable. The Three-Parties Alliance was succeeded in government by the Third Force, which comprised the Democratic and Socialist Union of the Resistance (UDSR), the SFIO and the MRP, with the Gaullists and the Communists forming the opposition.