However, the political system was not one of open competition among candidates, although the PRM's rules required an open convention to select the candidate. Cárdenas established the unwritten rule that the president chose his successor. Cárdenas chose political unknown Manuel Ávila Camacho, far more centrist than Múgica, as the PRM's official candidate. He was "known as a conciliator rather than a leader" and later derided as "the unknown soldier." Múgica withdrew, realizing his personal ambitions would not be satisfied, and went on to hold other posts in the government. Cárdenas may well have hoped Ávila Camacho would salvage some of his progressive policies and be a compromise candidate compared to his conservative opponent, General Juan Andreu Almazán. Cárdenas is said to have secured the support of the CTM and the CNC for Ávila Camacho by personally guaranteeing their interests would be respected.