L Legislature of the Mexican Congress

This 50th session of Congress consisted of senators and deputies who were members of their respective chambers.

For the first time in history a senator was elected who did not belong to the Institutional Revolutionary Party (PRI).

[1] Jorge Cruickshank García had been nominated by the PPS;[1] the PRI did not lose this seat, however, because it formed an electoral alliance with the winning party.

These were allocated in proportion to the votes that the non-winning parties obtained in the districts.

This reform, negotiated by Secretary of the Interior Jesús Reyes Heroles, included legal recognition of political organizations from the left, traditionally marginalized and pushed into armed struggle, especially after the events of 1968 and which degenerated into a "Dirty War" during the 1970s.