WASHINGTON -- The White House has laid the groundwork to place more conservatives on the Supreme Court, scrutinizing the backgrounds and legal views of a shrinking list of candidates amid speculation that ailing Chief Justice William H. Rehnquist soon will step down.
Keenly aware that a chapter of President Bush's legacy is at stake, conservative and liberal advocacy groups are preparing for what both sides believe will be an intense confirmation fight.
Court specialists expect that Rehnquist, who is battling thyroid cancer, will leave by the end of June when the current court session concludes.
''The vacancy could come anytime after this Memorial Day weekend, we think," said Sean Rushton, director of the conservative Committee for Justice, which has close ties to the White House counsel's office.
''They have been winnowing the list down for some time now. I imagine they're down to maybe three or five -- a handful anyway -- who are their first choices," he said.
White House officials say it is inappropriate to discuss filling a vacancy that does not exist. They refuse to disclose publicly any details about how Bush might pick the first nominee for the court in more than a decade.
But those tracking the process say the counsel's office has researched the resumes of prospective justices, their court opinions, and their views about constitutional law.
Justice Department lawyers are carefully looking into the personal backgrounds of possible nominees. Justice Clarence Thomas was confirmed despite allegations of sexual harassment. One of President Reagan's nominees, Douglas H. Ginsburg, withdrew from consideration after it was revealed that he had smoked marijuana.
John O. McGinnis, a law professor at Northwestern University and former deputy assistant attorney general in the Justice Department's office of legal counsel, said he thinks Bush might have made up his mind.
''This White House -- I congratulate it on its ability to be secret," McGinnis said. ''It's entirely possible that Rehnquist has already communicated his intention to step down and the White House has a plan absolutely set."
Liberals hope Bush will fill his first vacancy with a centrist, a consensus candidate, instead of one who would please right-wing Republicans who were instrumental in the president's reelection. But they acknowledge that may be wishful thinking.
Bush has shown he is willing to stick by his nominees. When Senate Democrats denied votes on 10 of his picks for the federal bench, the president did not back down. Instead, he sent the same group of conservatives back to the Senate. That set the stage for the recent showdown over the filibuster, a political maneuver the Democrats used to stall the votes through protracted debate.
''On every occasion the president has chosen confrontation rather than consultation and consensus, so we assume it's going to be confrontation one more time -- or four more times, depending on what happens," said Ralph G. Neas, director of the People for the American Way. The liberal group has worked to block several of President Bush's appointments to the courts
Central to the filibuster fight was the prospect of Bush's selecting a new Supreme Court justice. Neither side was completely satisfied by a compromise that ended the internal Senate battle last week.
The left complained it opened the way for the confirmation of nominees outside the judicial mainstream. Conservatives said it seemed to preserve the Democrats' right to block a Supreme Court nominee.
If Rehnquist steps down, it could be just the beginning of Bush's chance to put his imprint on the court before his term ends in early 2009.
Justice John Paul Stevens turned 85 in April. Justices Sandra Day O'Connor and Ruth Bader Ginsburg are in their 70s.
Bush has suggested that he favors the views of Justices Thomas and Antonin Scalia. Both believe the Constitution should be interpreted literally and that judges should not be swayed by changes in political or social culture.
Liberals predict a major fight if Bush nominates someone in the mold of Thomas and Scalia, or anyone viewed as too conservative.
''If he [Bush] puts a nominee up whose record is hostile to individual rights, this administration will be igniting a firestorm of opposition around the country," said Nan Aron, director of the Alliance for Justice, which helped block the confirmation of Robert H. Bork to the Supreme Court in the late 1980s.
''I think it will be a fight that will shape our lives for decades," she said.