PNR Founded by Calles — One-Party State Institutionalized

Former President Plutarco Elías Calles founded the Partido Nacional Revolucionario (PNR) on March 4, 1929 as a mechanism to institutionalize power after the assassination of President-elect Obregón (1928) and manage a succession of 'the Maximum Chief' (Jefe Máximo). The PNR unified regional military chiefs, labor unions, and agrarian organizations under one party umbrella. Renamed PRM in 1938 and PRI in 1946, this party would hold unbroken power for 71 years.