If the challenges to the ecology of oil posed by the revolutionary state did not yield fruit, it would seem that a labor force devastated since 1921 could hardly do better. That impression, however, is mistaken. Ten years of intensive political education had left a deep imprint in the workers and their work culture. At the same time, the weakness of the revolutionary state meant that even if Mexico City had lost patience with radicals, local authorities could be flexible. Thus, workers who survived the 1921 debacle returned to the offensive in the mid-1920s. They made organizational advances and unionized the labor force at last. The emergence of political differences among the unions, however, meant that a significant minority failed to negotiate contracts and experienced the dissolution of their unions in the late 1920s. Key to the victories and the defeats were several local officials: the lawyer Emilio Portes Gil, the governor of Veracruz, Adalberto Tejeda, and the general Lázaro Cárdenas. Their intervention would have long-lasting consequences in the life of the unions.

The economic depression that engulfed the Mexican oil industry in the second half of the 1920s and merged into the Great Depression of the 1930s affected union activity as well. The unions split internally between those who wanted stability and a fringe that agitated for militancy. The Depression became a period of intense intraunion struggle in Tampico and the Huasteca, while a militant second generation of oil workers took over union leadership in new production sites in the Isthmus of Tehuantepec, Poza Rica, and Atzcapotzalco. In northern Veracruz the radicals' rise to leadership coincided with the ascent of Lázaro Cárdenas to the presidency in 1935.