Justice Sandra Day O'Connor has been the swing vote on many important decisions in the 24 years since President Reagan appointed her.
In her first term, O'Connor voted together with conservative Justice William Rehnquist on 27 of 31 decisions that were decided by a 5-4 vote.
But early on, she showed an independent streak. In her first term, the liberal wing of the court joined O'Connor in a 5-4 ruling declaring that a state-supported university in Mississippi could not exclude men from its nursing school.
O'Connor's role in some other cases:
1984: O'Connor writes a concurring opinion on nativity scenes that sets the legal standard for determining which displays violate the Constitution's prohibition on government establishment of religion.1989: O'Connor's opinion for the court declares that government programs violate equal protection when they set aside a fixed percentage of public contracts for minority businesses.1992: O'Connor and Justice Anthony Kennedy join a plurality opinion by Justice David Souter that criticizes the constitutional foundation for legalized abortion, while declining to overturn the 1973 decision that legalized it.2003: O'Connor co-authors the majority opinion upholding 5-4 the broadest restrictions on campaign donations in nearly 30 years.