Thorez died in 1964 and was succeeded as PCF leader by Waldeck Rochet. In May 1968 widespread student riots and strikes broke out in France. The PCF supported the general strike but opposed the revolutionary student movement, which was dominated by Trotskyists, Maoists and Anarchists and the so-called "new social movements" (including ecologists, gays movements, prisoners' movement — see Michel Foucault, etc.). The PCF also alienated many on the left by supporting the Soviet invasion of Czechoslovakia in August 1968. Nevertheless, the PCF benefited from the left-wing mood of the period, and from the collapse of the socialists. Due to Waldeck Rochet's ill health, Jacques Duclos was the candidate at the 1969 presidential election. Duclos polled 21% of the vote, completely eclipsing the SFIO whom, represented by Gaston Defferre, arrived fourth at the first turn. Gaullist Georges Pompidou won against Alain Poher (center right) at the second turn.

In 1970, Roger Garaudy, a member of the Central Committe of the PCF from 1945 on, was expelled from the party for his revisionist tendencies, being criticised for his tentative to reconcile Marxism with Roman Catholicism. Starting in 1982, Garaudy emerged as a major Holocaust denier and was effectively condemned in 1998.

In 1972 Waldeck Rochet was succeeded by Georges Marchais, who had effectively controlled the party since 1970. Marchais began a moderate liberalisation of the party's policies and internal life, although dissident members, particularly intellectuals, continued to be expelled. The PCF entered an alliance with François Mitterrand's new Socialist Party (PS), but broke it off again before the 1974 legislative elections, allowing the right to retain power.

Nominally the French communists supported Mitterrand's candidacy in 1974 presidential election, but the Soviet ambassador to Paris and the director of L'Humanité did not hide their satisfaction with Mitterrand's defeat. According to Jean Lacouture, Raymond Aron and François Mitterrand himself, the Soviet government and the French communist leaders had done everything in order to prevent Mitterrand from being elected: they regarded him as too anti-communist and too skilful in his strategy of rebalancing the Left on account of PCF. During Mitterrand's term as PS first secretary, the socialists re-emerged as the principal party of the left.

In 1976, the PCF abandoned the reference to the soviet model and began to follow a line closer to that of the Italian Communist Party's eurocommunism. However, this was only a relative change of direction, as the PCF globally remained loyal to Moscow, and in 1979, Georges Marchais supported the invasion of Afghanistan.

The alliance with the PS was renewed for the 1981 elections, at which Mitterrand was elected President and the left won a large majority in the National Assembly. At the first turn, Valéry Giscard d'Estaing (UDF, center-right) made 28.31% of the votes, François Mitterrand (PS 25.85%, Jacques Chirac (RPR, right-wing) 17.99%, and Georges Marchais came in fourth with 15.34% of the votes (environmentalist Brice Lalonde and trotskyist Arlette Laguiller, from Lutte Ouvrière, both made less than 4%). Mitterrand won at the second round with 51.76% against 48.24% for Valéry Giscard d'Estaing.

Under Mitterrand the PCF held ministerial office for the first time since 1947, but this had the effect of locking the PCF into Mitterrand's reformist agenda, and the PCF's more moderate supporters drained away to the PS. The PCF also suffered from the rise of the National Front led by Jean-Marie Le Pen, whose populist slogans appealed to some PCF voters. During the 1980s the PCF vote fell sharply.

The fall of the Soviet Union in 1991 led to a crisis in the PCF, but it did not follow the example of some other European communist parties of dissolving itself or changing its name. In 1994 Marchais retired and was succeeded by Robert Hue. Under Hue the party embarked on a process called la mutation. La mutation, which included the thorough reorganization of party structure and to move away from Leninist dogmas, was intended to vitalize the stagnant left and to attract non-affiliated leftists to join the party. But in effect it only resulted in increasing the pace of the decline of the party. Under Lionel Jospin, the PCF again held ministerial offices from 1997 to 2002 (Jean-Claude Gayssot as Minister of Transportation, etc.). The party became riddled with internal conflict, as many sectors opposed la mutation and the policy of co-governing with the Socialists.


Hue only received 3.4% of the votes in the 2002 presidential elections. At the 2002 legislative elections, the PCF arrived fourth, polling 4.8% of the vote (the same as the center-right UDF) and won 21 seats (out of 567). Chirac's UMP came in first, followed by the Socialist Party, the National Front, UDF, PCF, the Greens, and then the trotskyist Revolutionary Communist League (LCR) and Lutte Ouvrière. Eventually Robert Hue had to resign, and in 2003 Marie-George Buffet took over the leadership of the party. Under Buffet the party embarked on a process of reconstruction, reversing some of the moves done during la mutation.

On proposed European constitution issue, French communists fought alongside extreme left-wing groups, half of the Socialist Party, the Greens, and right wing eurosceptics for 'no'. The victory of the 'No' in the 2005 French plebiscite on the Treaty establishing a Constitution for Europe (TCE), along with the campaign against the Bolkestein directive, served as a major boost for the party. Under the referendum campaign the party was vitalized, with a resurgence of the work in the party cells. The PCF's retains some strength in the Paris suburbs, in the industrial areas around Lille, and in some areas of the south such as Marseille.

In 2005, the social conflict at the SNCM in Marseilles, then the 4 October 2005 demonstration against the New Employment Contract (CNE) marked the opposition to Dominique de Villepin's right-wing government, whom shared his authority with Nicolas Sarkozy as Ministry of Interior, leader of the UMP right-wing party, and probable contender for the 2007 presidential election. Marie-George Buffet also heavily criticized the government's response to the riots in autumn, speaking of a deliberate "strategy of tension" employed by Sarkozy whom called the youth from the housing project "scum" (racaille) which needed to be clean-up with a "Kärcher" high pressure cleaner. While most of the Socialist deputies voted for the instauration of the state of emergency during the riots, which lasted until January 2006, the PCF, along with the Greens, opposed itself to it.

2006 was marqued by the protests against the First Employment Contract, which finally forced president Chirac to repeal the controversed law aimed at "flexibilizing" labour law.