1920s: In 1920 Mexico's Partido Nacional Revolucionario (PNR), the National Revolutionary Party, is founded out of a coalition of military, labor, and peasant leaders. The party takes a conservative approach to the reforms demanded by socialist revolutionaries, seeking economic and political stability above social justice. According to the government that is established, the president of Mexico can only serve one term but chooses his successor, creating a one-party democracy.

1990s: The PNR, renamed PRI (Partido Revolucionario Institucional, the Revolutionary Institutional Party) has ruled Mexico for seventy years, holding the presidency and both legislative houses. In 1997 the PRI lost the lower legislative house for the first time in what has been called the "freest election in Mexican history." The PRI still holds the upper house and the presidency.

1920s: The capitalist PNR slowly and ineffectively implements the socialist policy of land reform—the redistribution of...