In the Center, Hers Was the Vote That Counted

Her opinions were an exercise in keeping her options open; they would often contain qualifications or exceptions that reappeared in later cases as her rationale for reaching a seemingly different result on a similar issue.

And, when she was the fifth member of a majority, she sometimes issued a concurring opinion that articulated a narrower basis for the decision -- and became the de facto controlling precedent.

In 1985, O'Connor articulated a case-by-case "endorsement" test for deciding whether a given governmental action in support of religion violated the Constitution. According to O'Connor, the First Amendment's ban on the establishment of an official religion meant that governments could not advance or endorse religion.

The phrase "under God" in the Pledge of Allegiance, and a Cleveland program that gave parents government money to send their children to parochial schools, passed constitutional muster with her, while the posting of the Ten Commandments in a county courthouse or on the Texas Capitol grounds could not.

She generally voted for conservative positions on crime, economic regulation and, especially, states' rights. Among the federal laws O'Connor voted to strike down as violating state sovereignty were one that barred the carrying of a firearm within 1,000 yards of a school, a provision of the Americans With Disabilities Act permitting disabled state employees to sue their bosses for discrimination, and a provision of the Violence Against Women Act that let rape victims sue their attackers in federal court.

In her last term on the court, O'Connor dissented in a 6 to 3 ruling that gave the federal government the power to override California's state law permitting the use of homegrown "medical marijuana."

Noting that she would have voted against legal marijuana if she were a Californian herself, O'Connor faulted the court for "stifl[ing] an express choice by some States, concerned for the lives and liberties of their people, to regulate medical marijuana differently."

Yet O'Connor's backing for states' rights was not unlimited. She would not let it become a means to roll back what she saw as the core social advancements of the 1960s and '70s.

Two years ago, she voted with the majority to uphold the right to sue state employers for violating the federal Family and Medical Leave Act, in a case widely seen as a test of gender equality in the workplace.

In 2004, she joined the liberals in a 5 to 4 ruling that said states could be sued under the disabilities act if they fail to make their courthouses accessible to the handicapped.

And on abortion and race, O'Connor, after expressing many Americans' second thoughts about the social changes of the '60s and '70s, ultimately decided not to undo them.

In 1983, the court, citing Roe v. Wade , struck down an Akron, Ohio, ordinance that put regulations on abortion, including a required 24-hour waiting period. O'Connor dissented, offering some critical words about Roe .