Institutional Revolutionary Party
The Institutional Revolutionary Party (, 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 (, PNR), then as the Party of the Mexican Revolution (, PRM), and finally renaming itself as the Institutional Revolutionary Party in 1946.
Mexico
Three parties have historically been the dominant parties in Mexican politics: the National Action Party: a conservative party founded in 1939 and belonging to the Christian Democrat Organization of America; the Institutional Revolutionary Party, a center-left party and member of Socialist International that was founded in 1929 to unite all the factions of the Mexican Revolution and held an almost hegemonic power in Mexican politics since then; the Party of the Democratic Revolution: a left-wing party, founded in 1989 as the successor of the coalition of socialists and liberal parties.