Columbia subject headings:
Elections--Mexico.
Mexico--Politics and government.
Political parties--Mexico.
Harvard subject headings:
Elections--Mexico--History--20th century.
Mexico--Politics and government--1988-
Political parties--Mexico--History--20th century
Princeton subject headings:
Elections--Mexico--History--20th century.
Mexico--Politics and government--1988-2000.
Political parties--Mexico--History--20th century.