Mexicans in Chihuahua protest electoral fraud, 1985-1988
The Institutional Revolutionary Party (PRI) had controlled Mexico and won almost every presidential, gubernatorial, and senatorial election since its founding in 1929. The PRI also dominated politics in most municipalities and on local levels. In the 1983 and 1985 elections however, the National Action Party (PAN) won many municipal seats and posed a significant challenge to state offices held by the PRI.