AS PRESIDENT BUSH EXAMINES HIS Supreme Court options, he almost certainly understands that a year from now, his performance will be evaluated mainly on whether he confirmed the unelected Court's centrality in American politics, or took a historic first step in beginning to curb that centrality.

A year from now, he will have had two openings to fill--the seats of Justice Sandra Day O'Connor and of Chief Justice William Rehnquist, who is unlikely to attempt to preside over another full term. At the moment no one else on the Court seems inclined to retire, and Bush may never see a third opening. Since the first term of Richard Nixon, no president has had to fill more than two vacancies in a single four-year term.

The situation Bush faces now is similar to what Bill Clinton faced in 1993-94. One conservative and one liberal retired then, one conservative and one liberal are retiring now. Clinton used his picks to push the Court one click to the left. Picking liberals Ruth Bader Ginsburg and Stephen Breyer to replace conservative Byron White and liberal Harry Blackmun meant a 5-4 majority to uphold Roe v. Wade became 6-3. It meant a 5-4 majority against gay rights became 5-4 in favor (eventually 6-3 when Justice O'Connor added icing to the cake by reversing her 1986 position in 1996). By almost any calculation, it was very good news for the liberal cause on a range of other issues, including affirmative action, capital punishment for minors, and prayer in public places.

If a year from now Bush has won confirmation for two conservatives, regardless of who the new chief justice is, the pro-Roe majority goes from 6-3 back to 5-4, with at least an outside chance of pro-life forces prevailing on the parental notification case to be decided in the coming term; a probable 5-3 majority for removing "under God" from the Pledge of Allegiance will become an inconclusive 4-4 (Justice Antonin Scalia has recused himself from voting on this issue); and the survival of racial preferences in universities and elsewhere would be in serious doubt.

Equally important would be the impact of such a shift on the psychology of the Court and its politics. Much of politics is momentum. The momentum of the Court toward being a pivotal political power center, rivaled only by the presidency, was resented by Dwight Eisenhower. It was actively fought in the administrations of Richard Nixon and Ronald Reagan. But both these presidential fights failed because an elective institution, in each case a Democratic-controlled Senate, inflicted devastating rebukes to the White House in 1969, 1970, and 1987. The nominees who filled the seats intended for Clement Haynsworth and G. Harrold Carswell (Nixon) and Robert Bork (Reagan) were Harry Blackmun and Anthony Kennedy. Both these men, after an interval of ambiguity, joined the liberal wing of the Court, confirming and raising the morale of the Court in its drive to power.

How did the Court become so politicized? At times in the past, the Court reached for power and found itself thwarted by strong presidents using their elective mandates--Jackson, Lincoln, arguably Franklin Roosevelt in his court-packing campaign in the 1930s, which ended in a kind of stalemate, with the Court maintaining a degree of independence while tacitly ending its campaign to invalidate the New Deal.