Centrism has a specific meaning within the Marxist movement, referring to a position between a revolutionary and reformist position. For instance, the Independent Social Democratic Party of Germany (USPD) and Independent Labour Party (ILP) were both seen as centrist because they oscillated between advocating reaching a socialist economy through reforms and advocating revolution. The parties that belonged to the "so-called" Two-and-a-half and Three-and-a-half Internationals, who could not choose between the reformism of the social democrat Second International and the revolutionary politics of the Communist Third International, were also exemplary of centrism in this sense. They included the Spanish Workers' Party of Marxist Unification (POUM), the ILP and Poale Zion.
For Trotskyists and other revolutionary Marxists, the term "centrist" in this sense has a pejorative association. They often describe centrism in this sense as opportunistic, since it argues for a revolution at some point in the future, but urges reformist practices in the meantime. Libertarian socialists and anarchists also tend to view any reformism as political opportunism because they view reformism as being incapable of effecting structural changes to social organization.
The term "centrism" also denotes positions held by some of the Bolsheviks during the 1920s. In this context, "centrism" refers to a position between the Right Opposition, which supported the New Economic Policy and friendly relations with capitalist countries, and the Left Opposition, which supported an immediate transition to a socialist economy and world revolution. By the end of the 1920s, the two opposing factions had been defeated by Joseph Stalin, who eventually gained enough support from members of both factions through the application of various ideas formulated by the factions' various leaders, notably Leon Trotsky and Nikolai Bukharin.