In the elections of 1940, Cárdenas, hoping to prevent another uprising or even "an outright counter-revolution throughout the Republic" by those opposed to his leftist policies, endorsed the PRM nominee Manuel Ávila Camacho, a moderate conservative. "Obregonista" Francisco Múgica would have been Cárdenas's ideological heir, and he had played an important role in the Revolution, the leader of the left-wing faction that successfully placed key language in the Constitution of 1917, guaranteeing the rights of labor. Múgica had known Cárdenas personally since 1926 when the two were working in Veracruz. Múgica had served in Cárdenas's cabinet as Secretary of the National Economy and as Secretary of the Ministry of Communications and Public Works. In those positions, Múgica made sure the federal government pursued social goals; Múgica was considered "the social conscience of Cardenismo." Múgica resigned his cabinet post to be a candidate for the 1940 presidential election.