President Bush stepped to the plate Monday to nominate a replacement for Justice Sandra Day O'Connor. He leads a party with 55 votes in the Senate and has just appointed to the Supreme Court a conservative chief justice widely hailed as one of the most qualified nominees in recent memory.

The president swung and missed.

His choice of his counsel, Harriet Miers, passes up a rare opportunity to change the direction of the Supreme Court. O'Connor provided decisive votes for affirmative action in colleges and universities, against bans on partial-birth abortion, against posting of the Ten Commandments in public spaces, and for the legal recognition of gay rights. Miers has no record on these and similarly controversial issues of constitutional law.

Although initially uneasy, conservatives rallied around John Roberts because of his outstanding record and the people he'd worked for. Liberals in favor of using the Supreme Court to decide social issues usually do not work for the likes of William Rehnquist, William French Smith, Fred Fielding and Kenneth Starr.

Miers, by contrast, has no track record on constitutional law. Her lack of service as a judge means that there is no evidence on how she would interpret the Constitution or apply it to specific cases. Her only claim to being a legal conservative — that the courts should generally refrain from intervening in controversial social policies — is her service as a close personal aide to Bush. Less than one year of that service was as White House counsel; the rest has been as staff secretary (the person who controls paper flow to the president) and deputy White House chief of staff. By all accounts, Miers distinguished herself as a loyal, dedicated and hard-working aide. But, according to press reports, she did not win a reputation as a forceful conservative on issues such as the administration's position on stem cell research or affirmative action.

Conservative Republicans will remain in mourning that Bush refused to elevate one of the many talented, principled believers in judicial restraint on the lower courts. Miers does not come off Bush's deep bench of conservative appellate judges.

And the president's supporters have other reasons to be unhappy with this choice. The president campaigned on the promise to appoint judges in the mold of "a Scalia or Thomas." To Republicans, this suggested a nominee with well-known, defined views on the importance of the separation of powers and federalism, and on the need for restrictions on judicial freelancing on such matters as the meaning of privacy or due process. Miers may prove to agree with Justices Antonin Scalia or Clarence Thomas, but conservatives have no reason to think so. She appears to have few public views on any issue of constitutional law, unlike previous nominees Scalia, Thomas and Robert Bork.

Another red flag for conservatives may be what is regarded as Miers' strongest credential: her work with the organized bar. Miers was elected president of the Texas bar and was a mover and shaker in the American Bar Association. Republicans have long criticized the ABA for politicizing the professional bar by taking positions on controversial social issues such as abortion and providing politically biased evaluations against Reagan-Bush judicial nominees. To be sure, Miers reportedly fought to allow the general membership to vote on the ABA's position supporting the right to abortion, a fact much trumpeted by Bush administration supporters Monday. But she also apparently urged that the White House preserve the ABA's privileged role in reviewing the qualifications of judicial nominees.

There are some entirely welcome aspects to Miers' appointment. The appointment of a woman matters a great deal to an administration that has been careful to promote women and minorities through federal appointments. Because she has not come up through lower courts, she may help move the Supreme Court away from its technocratic attitude toward law, its blindness to political reality through claims of supremacy in interpreting the Constitution, and its squabbling through a multitude of separate opinions.

Two other issues could win her more support in her own party, but ironically, she may be unable to discuss them because of the Bush administration's devotion to government secrecy. First, Miers may have wanted to break the Democrats' use of the filibuster to block confirmation of Bush's lower court judges. Second, she may be one of the key supporters in the Bush administration of staying the course on legal issues arising from the war on terrorism. But it is hard to see how the administration could reveal Miers' position on these issues, given its tough, five-year struggle to preserve the confidentiality of executive-branch deliberations.

Miers is almost certain to be confirmed. She is not likely to prove a revolutionary conservative, though, but rather a gradualist judge, keen to balance conflicting values rather than declaring clear principles.

John Yoo, a law professor at the University of California at Berkeley and a visiting scholar at the American Enterprise Institute, is the author of "The Powers of War and Peace." He wrote this commentary for The Washington Post.