During the administration of Echeverría, a new Federal Election Law was approved: 
Lowered the number of members a party needed to become officially registered from 75,000 to 65,000
Increased the number of Congress seats chosen according to proportional representation principle from 20 to 25
Introduction of a permanent voting card
Established the age of candidacy at 21, from 30.

Following the PRI tradition, Echeverría handpicked his successor for the Presidency, and chose his Finance Minister and childhood friend, José López Portillo, to be the PRI Presidential candidate for the 1976 elections.
Due to a series of events and an internal conflict in the opposition party PAN, López Portillo was the only candidate in the Presidential election, winning unopposed.
During the administration of Echeverría, a new Federal Election Law was approved: 
Lowered the number of members a party needed to become officially registered from 75,000 to 65,000
Increased the number of Congress seats chosen according to proportional representation principle from 20 to 25
Introduction of a permanent voting card
Established the age of candidacy at 21, from 30.
Following the PRI tradition, Echeverría handpicked his successor for the Presidency, and chose his Finance Minister and childhood friend, José López Portillo, to be the PRI Presidential candidate for the 1976 elections. Due to a series of events and an internal conflict in the opposition party PAN, López Portillo was the only candidate in the Presidential election, winning unopposed.
Luis Echeverría