WASHINGTON – The Democratic minority leader of the U.S. Senate said yesterday that he will vote against President Bush’s nominee for chief justice, Judge John Roberts Jr., because of concerns over memos that the nominee wrote as a young lawyer in the Reagan administration and because of the unwillingness of the White House to release documents he wrote while working for the solicitor general.

The announcement by Senator Reid, a Democrat of Nevada, is a strong sign that the 50-year old Circuit Court judge will not be confirmed by the wide majority some had expected. It also suggests that Democrats are likely to oppose any nominee that Mr. Bush sends their way. Republicans said the move provides an opening for the president to nominate a strong conservative, including judges who were previously filibustered by Democrats.

“This sends the message that, certainly among the Democratic leadership in the Senate, every conservative is as bad as any other and that they are still wedded to an obstructionist policy,” the executive director of the Committee for Justice, Sean Rushton, said. “The president might as well pick somebody who represents his philosophy and the views of his base because any nominee is going to be opposed.”

Mr. Reid asked his colleagues in July to withhold their judgment on Judge Roberts until after his confirmation hearing. Some have said that the request may have drained momentum from the nominee’s opponents, many of whom seemed disarmed during a hearing in which Judge Roberts won praise from Democratic members of the Senate’s judiciary committee and emerged largely unscathed after nearly 20 hours of questions.

Democrats met yesterday morning to discuss strategy before a judiciary committee vote on Judge Roberts tomorrow. Mr. Reid emerged from the meeting saying he will vote against the nominee because he did not distance himself from memos that defended administration policy on civil rights, voting rights, and women’s rights. Judge Roberts said last week that the memos did not necessarily reflect his personal views. Mr. Reid said he was not convinced by that response.

“Anyone who has read the memos can see that Roberts was expressing his own personal views on these important policy matters,” Mr. Reid said. “In memo after memo, the text is clear. It is simply not plausible for the nominee to claim that he did not share the views that he expressed.”

The president is expected to name a judge to replace Justice O’Connor in the coming days, and there was some speculation yesterday that Justice Stephens will retire next year.

A spokesman for Mr. Reid said Democrats will not necessarily follow the leader in the vote on Judge Roberts. “In the end, it’s up to each and every member of the caucus to make their own decision,” the spokesman, Jim Manley, said. “But his decision does raise questions about the next nominee the White House sends up.”

Mr. Reid said yesterday that any nominee who is more conservative than Judge Roberts will be viewed by Democrats as “a poke in the eye with a sharp stick.”