The Partido Revolucionario Institucional (Institutional Revolutionary Party), more commonly referred to as the PRI, is Mexico’s oldest and arguably, most well-known political party. Until the start of the 21st century, the PRI was the sole hegemonic party in Mexico, governing without interruption from 1929 until 2000. 

Political scientists refer to the PRI as a “catch-all party,” a term used to describe pragmatic political parties that mutate their stances on multiple issues over time and may even have contradictory positions in different regions of the country. The PRI is usually midpoint-oriented (center in the economic left-right spectrum and neither conservative nor liberal in social terms), a strategy to attract voters. This strategic pragmatism enabled the PRI to develop a wide-encompassing political structure that incorporated many different groups, thus facilitating the party’s dominance in Mexican politics since its inception. 

Originally founded by President Plutarco Elias Calles in 1929 under the name Partido Nacional Revolucionario (National Revolutionary Party), the party evolved out of the Sonoran generals’ winning coalition from the Mexican Revolution (1910 – 1920).  During President Cardenas’ term in the 1930s, the party was renamed the Partido de la Revolución Mexicana (Mexican Revolutionary Party). By the 1940s, it finally adopted its current name under President Miguel Alemán. 

The PRI’s 71 years of uninterrupted rule came to an end when the PAN won the presidency, first in 2000 with the victory of Vicente Fox and then again in 2006 with the election of Felipe Calderón. The PRI did continue to hold a majority of governorships during those years, however. In 2012, the PRI returned to power with the election of Enrique Peña Nieto as president. 

In its first two years in office, the Peña Nieto administration proved successful at furthering the party’s agenda through Congress with the “Pact for Mexico” agreement between the PRI, the PAN, and the then-strongest left party, the PRD. Thirteen constitutional reforms were approved in key sectors and propelled the new government to a promising start. However, challenges regarding public security, allegations of human rights violations (most notably the disappearance of 43 students in Ayotzinapa in 2014), and various corruption scandals undermined voters’ confidence leading into the 2018 election. This election cycle resulted in the PRI's greatest defeat in history. The party lost not only the presidency but also two governorships (out of nine governorships up for election) and witnessed disappointing results in Congress and state legislature elections. 

Currently, the PRI holds 7.2% of the seats in the Senate (6 senators in total), 9.8% of the seats in the Chamber of Deputies (49 positions in total), and two out of 32 governorships (Coahuila and Durango).