The political legacy of Lázaro Cárdenas is marked by a striking paradox. On the one hand, Cárdenas as president of Mexico from 1934 to 1940 presided over the most radical phase of the Mexican Revolution or what some historians call the “Second Revolution.” He was instrumental in organizing industrial workers and peasants at the national level and incorporating both groups into the reorganized government party, the Partido de la Revolutión Mexicana (PRM), that had as its declared purpose the establishment of a “workers' democracy” in Mexico. Under his leadership the government supported the demands of industrial workers for higher wages and improved working conditions, greatly expanded the distribution of land to the peasantry, established new welfare programs, nationalized the railroad and petroleum industries and inaugurated a program of socialist education in the public schools. The prestige of Cárdenas as the foremost leader of the radical phase of the Revolution was enhanced by the fact that he, unlike many of his contemporaries, never attempted to use political office for personal financial gain; he was not a rich man when he completed his term of office as president. At the time of his death in 1970, Cárdenas was eulogized as “the greatest figure produced by the Revolution… an authentic revolutionary who aspired to the greatness of his country, not personal aggrandizement.” On the other hand, Cárdenas was the architect of the corporatist system of interest representation, including labor, peasant and business organizations, that provided the institutional framework of what Crane Brinton has called the “Thermidor,” i.e., the conservative reaction to the radical phase of the revolutionary process, that began in Mexico in approximately 1940. The institutions developed by Cárdenas were utilized by his successors to curtail the very reforms, such as agrarian and labor reform and socialist education, that had been central to his reform program. Moreover Cárdenas facilitated the transition to a more conservative era by naming as his successor Manuel Ávila Camacho, who was known to favor a moderation of the reform process, rather than Francisco Múgica, the preferred candidate of the radicals in the government. In short, Cárdenas played a decisive role both in presiding over the radical phase of the Revolution and in launching and shaping the relatively conservative post-1940 era. The paradox of the political legacy of Cárdenas is that though the seemingly radical reforms he carried out had a lasting impact upon Mexican politics, the impact was predominantly conservative rather than radical. This essay will endeavor to explain the paradoxical political legacy of Lázaro Cárdenas by focusing upon his ideology, the institutional reforms he carried out while president, and the impact of those reforms after 1940.