In one sense, Sandra Day O’Connor became the most powerful woman in America by accident. If the Supreme Court had not been so sharply divided between liberal and conservative blocs, she would not have provided the key vote on so many critical issues during her 24 years on the bench.

But in another sense, her impact was no accident at all. As the nation’s political life grew increasingly polarized, O’Connor acquired influence by being a pragmatic, reasonable consensus builder. As a result, in 77 percent of the recent Supreme Court cases decided by a 5-4 vote, she joined the majority far more than any other justice.