At the end of the presidency of Lazaro Cardenas (1934-40) - thirty years after the beginning of the Mexican revolution-the Mexican working class was organized as never before into a large and powerful union confederation, the Confederacion de Trabajadores de Mexico (CTM). Within this organization, the Communists and other independent leftists controlled a sizeable following. However, in a series of dramatic confrontations and purges in the ranks of organized labor, between 1946 and 1949, the Left and the labor militants were decisively defeated. The culmination of these struggles between union militants and the Left, on the one hand, and the moderate, progovernment leadership on the other, was the socalled charrazo of 1948, when the Mexican government intervened in the railway workers' union to impose a conservative leadership. The charrazo and similar, related events within the CTM and in other important industrial unions led to organized labor falling under the domination of a small camarilla of trade union leaders, the so-called cinco lobitos, who saw their task as that of ensuring labor discipline and providing political support for the ruling party, the Partido Revolucionario Institucional (PRI, formerly the PRM), and its economic project. For most of the postwar period, Mexico's relatively tranquil industrial relations provided an underpinning for the rapid economic growth and political stability that defined the Mexican “miracle.”

The formation of the CTM in 1936 was one of the great events of the Cardenas presidency and of the history of the Mexican working class.