The Bush administration is preparing to abandon a half-century tradition in which presidents have relied on the American Bar Association for advice about prospective federal judges, angering congressional Democrats who are portraying the move as an effort to fill U.S. court vacancies on a more ideological basis.

According to government sources, White House counsel Alberto R. Gonzales intends to inform the bar association's president tomorrow that White House and Justice Department officials will no longer consider the views of an ABA screening committee before sending judicial nominations to the Senate.

The ABA's unique role as early arbiter of the professional qualifications of candidates for the federal judiciary -- ranging from district courts to the Supreme Court -- has long irritated conservatives in Congress and in legal circles. Republicans, who have mounted a sustained campaign in recent years to put what conservatives call less "activist" jurists on the bench, say the nation's largest legal organization has a liberal tilt -- a view that ABA officials and many Democrats dispute.

Yesterday, White House officials were reluctant to publicly discuss the pending decision or its rationale. "If there's anything to announce, we will do so after the White House counselor's meeting with ABA officials," said Scott McClellan, a spokesman for President Bush.

But a source familiar with the administration's thinking said that Bush aides believe the ABA should not have a greater say than any other organization about the merits of judicial candidates. The bar association "should be involved in the process" after the nominations reach the Senate, the source said, "but it should not be a special role."

Word of the White House's position, first reported in the New York Times, prompted a pair of Senate Democrats to write a letter of protest to the president on Friday. Calling the ABA's evaluation "the gold standard by which judicial candidates are judged," Senate Judiciary Committee members Patrick J. Leahy (Vt.) and Charles E. Schumer (N.Y.) wrote that the administration's move would "dilute the quality of the federal bench" and "further polarize a process that, by now, all senators agree cries out for less partisanship."

The White House's effort to diminish the bar association's influence is the latest phase of the increasing antagonism between Democrats and Republicans over the selection of federal judges.

Republicans began to object to the ABA's role in 1987, when four members of the association's 15-member Standing Committee on the Federal Judiciary suggested that Judge Robert H. Bork was not well-suited for the Supreme Court vacancy to which President Ronald Reagan had nominated him.

More recently, President Bill Clinton complained that the GOP-led Senate refused to confirm -- and, in some cases, even convene hearings on -- his judicial nominees, producing what he called a crisis of vacancies in the courts.

In the weeks since Bush took office, Gonzales and a team of White House and Justice Department lawyers, including several prominent conservative critics of Clinton, have begun to act swiftly to fill the nearly 100 judicial vacancies that the new administration inherited. Working at times into the evening, the team has already interviewed more than 50 candidates, according to an administration source. It is unclear how soon the president will send nominations to the Senate.

The bar association has played an unofficial but prominent role in evaluating potential judges since 1948, when it began to advise the Senate. Four years later, President Dwight D. Eisenhower invited the association to give him ratings of candidates' professional qualifications, in a bid to help insulate the process from political pressure.

Patricia M. Hynes, a New York lawyer who is the screening committee's chairman, noted yesterday that the panel has worked on behalf of nine presidents from both parties by confidentially interviewing the colleagues of prospective nominees to gauge their competence, integrity and temperament. The committee, Hynes said, "does not take into account any political affiliations or philosophies or ideologies. It does not happen."

Schumer said in an interview that he was contacted a few days ago by ABA members, whom he declined to identify, who had become "worried" after learning from Bush aides that the association's role was about to be curtailed.

Such a change in the White House, Schumer said, "gives a signal that, instead of quality, they are looking for ideology. That is just not going to sit well, particularly with a president who campaigned on bipartisanship." He predicted that Senate Democrats would continue to solicit the ABA's advice.

The ABA's president, Martha W. Barnett of Tallahassee, said, "I've had no indication personally" that her meeting with Gonzales tomorrow afternoon will be anything more than a routine forum for getting acquainted with the new administration. But after becoming aware of the message that Gonzales plans to relay, she said: "It strikes me as a very shortsighted decision."

White House counsel Alberto R. Gonzales will inform the ABA about its diminished role, sources say.