Excerpts from Books and Wikipedia
"The Institutional Revolutionary Party (Spanish: Partido Revolucionario Institucional, PRI) is a Mexican political party founded in 1929 that held uninterrupted power in the country for 71 years from 1929 to 2000, first as the National Revolutionary Party (Spanish: Partido Nacional Revolucionario, PNR), then as the Party of the Mexican Revolution (Spanish: Partido de la Revolución Mexicana, PRM) and finally as the PRI in 1946. The PNR was founded in 1929 by Plutarco Elías Calles, Mexico's paramount leader at the time and self-proclaimed Jefe Máximo (Supreme Chief) of the Mexican Revolution. The party was created with the intent of providing a political space in which all the surviving leaders and combatants of the Mexican Revolution could participate and to solve the grave political crisis caused by the assassination of President-elect Álvaro Obregón in 1928. Although Calles himself fell into political disgrace and was exiled in 1936, the party continued ruling Mexico until 2000, changing names twice until it became the PRI. After losing the Presidency in the 2000 elections, the PRI held most of the state governments and had strong performances at the local levels;" [Wikipedia]