Legislative elections were held in Mexico on 6 July 1997. The Institutional Revolutionary Party won 239 of the 500 seats in the Chamber of Deputies, the first time it had failed to win a majority. As a result, the leaders of the Party of the Democratic Revolution and of the National Action Party were able to control Congress and installed PRD member Porfirio Muñoz Ledo as the president of the Chamber of Deputies. At first, the PRI refused to accept the nomination and its parliamentary leader, Arturo Núñez Jiménez, declared it illegal. However, the PRI later accepted the fact and Muñoz Ledo answered the state of the union address of President Ernesto Zedillo.

The Party of the Democratic Revolution is a social democratic political party in Mexico. The PRD originated from the Democratic Current, a political faction formed in 1986 from the Institutional Revolutionary Party (PRI). The PRD was formed after the contested general election in 1988, which the PRD's immediate predecessor, the National Democratic Front, believed was rigged by the PRI. This sparked a movement away from the PRI's authoritarian rule.