The PNR Forms and Begins Seven Decades of One-Party Rule
After a president-elect's assassination, Plutarco Elias Calles builds a single party to absorb the revolution's rival factions
Quick facts
- Obregon assassinated
- 17 July 1928
- PNR founded
- 4 March 1929, by Plutarco Elias Calles
- Renamed PRM
- 1938
- Renamed PRI
- 1946
What happened
President-elect Alvaro Obregon, who had governed Mexico from 1920 to 1924 and won reelection in 1928 after Congress redefined the no-reelection rule to permit non-consecutive terms, was shot five times in the head by Jose de Leon Toral, a member of the Cristero movement opposed to the constitution's anti-clerical laws, on 17 July 1928, less than two weeks after his victory. The assassination threatened to fracture Mexico's revolutionary leadership into competing armed factions again, so former president Plutarco Elias Calles organized the Partido Nacional Revolucionario, founded on 4 March 1929 to unify the surviving leaders and combatants of the revolution under one political organization and guarantee peaceful transfers of power. The party was renamed the Partido de la Revolucion Mexicana in 1938 and, in 1946, the Institutional Revolutionary Party (PRI), the name it held through 71 consecutive years of rule until 2000.
Why it matters
The PNR's founding purpose, ending the pattern of assassination and armed rebellion that had killed Obregon and threatened to repeat itself, succeeded: Mexico avoided further civil war for the rest of the century, but at the cost of building a single-party system that would dominate Mexican politics without serious electoral challenge for seven decades.
How we know
The party's founding date, its organizing committee under Calles, and its later renamings are documented in Mexican institutional and academic historical sources; Obregon's assassination is independently documented in period U.S. and Mexican records held at the Library of Congress.
Sources
- The Mexican Revolution and the United States exhibit, Library of Congress. Obregon's Reelection and Assassination · Primary sourceloc.gov · The domain "loc.gov" is on our Primary source registry. · Link is live and its text matches the event's key terms (Jul 2026)
- Estudios de Historia Moderna y Contemporanea de Mexico, SciELO Mexico. Partido Nacional Revolucionario (PNR): Metodo y practica en la seleccion de candidatos a puestos de eleccion popular (1929-1938) · Peer-reviewed (author-declared)scielo.org.mx · Cited as a "journal" source (no stronger domain match). · Link is live and its text matches the event's key terms (Jul 2026)
- Library of Congress Country Studies. Mexico - The Maximato · General sourcecountrystudies.us · Cited as a "reference" source (no stronger domain match). · Link is live and its text matches the event's key terms (Jul 2026)
See something wrong? . Corrections with a source get fixed fastest.
Part of a timelineHistory of Mexico34 events · From the Olmec's colossal stone heads to a modern republic, told through the conquest that ended one empire and the revolution that remade the nation twiceView all →