Replacing the Swing Vote

The chief justice's chair that John G. Roberts Jr. occupied yesterday carries with it the titular leadership of the Supreme Court and the federal judiciary as a whole.

But as far as the actual decisions of the court go, Sandra Day O'Connor's seat is perhaps more critical. For years, O'Connor, 75, has been the court's swing vote on the moral and social issues that most inflame both left and right.

And that is why legal analysts are so closely scrutinizing White House counsel Harriet Miers, a former Texas lottery commissioner with little in the way of a paper trail, who was named to replace O'Connor.

Thanks to O'Connor, abortion rights have remained essentially intact, affirmative action in university admissions has survived and official support for religion has been limited to those expressions that can pass a complicated constitutional balancing test.

The 1981 appointee of President Ronald Reagan has moved steadily left in recent years, voting to strike down the death penalty for the mentally retarded and displays of the Ten Commandments on public property.

During the tenure of the late Chief Justice William H. Rehnquist, the nine-member court split between four generally liberal justices, three generally conservative ones and two moderate conservatives, O'Connor and Justice Anthony M. Kennedy, who usually voted with the conservatives but sometimes defected on social issues.

The substitution of one conservative, Roberts for Rehnquist, did not change that basic dynamic.

Replacing O'Connor with a committed conservative would create a 5 to 4 majority for the right on most issues as Kennedy is probably to the right of O'Connor.

Among the issues on which conservatives had hoped to see short-term change was abortion. The basic right to abortion, recognized in the 1973 case of Roe v. Wade , is not yet in play.

But the court will soon have opportunities to chip away at it. It will hear a case later this term on whether states must include a health exception in laws that require pregnant teenagers to notify their parents before seeking an abortion. And the Bush administration has asked the court to uphold a 2003 federal ban on the late-term abortion procedure called "partial birth" by critics.

The late-term abortion case offers the clearest instance of an issue on which O'Connor's vote would make the difference: In 2000, the court voted 5 to 4 to strike down a similar state ban. O'Connor voted with the four liberals in the majority.

Miers has no paper trail in part because she has no judicial experience -- unlike 61 of the 109 justices so far, including O'Connor, a former state judge.