The PAP has held the overwhelming majority of seats in Parliament since 1966, when the opposition Barisan Sosialis Party (Socialist Front), a left-wing group that split off from the PAP in 1961, resigned from Parliament, leaving the PAP as the sole representative party. In the general elections of 1968, 1972, 1976, and 1980, the PAP won all of the seats in an expanding Parliament.

Workers' Party Secretary General J.B. Jeyaretnam became the first opposition party member of Parliament in 15 years when he won a 1981 by-election. Opposition parties gained small numbers of seats in the general elections of 1984 (2 seats out of a total of 79), 1988 (1 seat of 81), 1991 (4 seats of 81), 1997 (2 seats of 83), and 2001 (2 seats of 84). Meanwhile, the PAP share of the popular vote in contested seats increased from 65% in 1997 to 75% in 2001. Since the opposition has contested less than half the seats in the last two elections, overall voter support for the PAP may be somewhat higher.