Sexenio is one of Mexico’s most important political institutions. It is the term limit on the Mexican Presidency, which limits the office holder to only one six-year term and is constitutionally barred from running for office again. It is important because it is one of the few significant limitations on executive power in Mexico, which is strong at Local, State, and National levels, and it is also seen as reaction to the failed experiment of re-election in Mexico in part of the Porfiriato era (1876–1911). Example: Partido Revolucionario Institucional rule of Mexico for most of the 20th century.