Conservative activists intensified their opposition to the Supreme Court nomination of Harriet Miers yesterday, launching two Web sites and planning radio and television advertising aimed at forcing her withdrawal.

The advocacy groups, which had expected to use their vast mailing lists and fundraising networks to support President Bush's Supreme Court nominees, instead are employing those tools to sow concern about Miers's conservative credentials and lack of judicial experience among their constituents outside Washington.

The public effort against Miers is supported by a wide range of well-known conservative figures and organizations, whose individual misgivings about the nomination have now coalesced into a coordinated effort to derail it.

Bush, speaking to reporters, again rallied to the defense of the troubled nomination, but he warned that he would not accede to requests from senators for documents detailing Miers's White House work. He said this would violate his right to receive confidential advice, but senators in both parties said the documents might allay concerns about her qualifications.

Some conservatives believe Bush could avoid this dispute by pulling the plug on the nomination.

"We've had three weeks here to try to sort out what kind of judge she is going to be," said Brian Burch, vice president of Fidelis, a Catholic antiabortion organization urging Miers's withdrawal. "We really do want to support the administration, but we just feel like we've reached a situation with this nomination that is beyond repair."

The campaign marks a dramatic escalation in the battle over her nomination that has fractured Bush's conservative base. While right-leaning columnists and publications, including George Will and the National Review, have called for her withdrawal, the new efforts are the first direct attempts at turning grass-roots conservatives against Miers.

"This kind of activity is unusual," said a Republican lawyer working with the White House to support Miers. "It's hard to know what the impact is yet. Some of that probably depends on what is happening outside the Beltway."

Bush sidestepped a question about whether the White House was preparing a "contingency plan" in case her nomination fails. "Harriet Miers is a fine person, and I expect her to have a good, fair hearing on Capitol Hill," he said.

On the question of documents, he said: "It's a red line I'm not willing to cross. . . . People can learn about Harriet Miers through hearings, but we are not going to destroy this business about people being able to walk into the Oval Office and say, 'Mr. President, here's my advice to you, here's what I think is important.' "

Sen. Arlen Specter (R-Pa.), chairman of the Judiciary Committee, urged the White House to be more forthcoming with "non-privileged documents." Such records, he said, might illuminate general areas in which Miers gave advice to the president but stop short of making her divulge the advice itself.

He said the White House should say whether Miers gave advice on subjects such as the treatment of detainees at Guantanamo Bay. "I believe that if Ms. Miers does well at her hearing that she can be confirmed without touching on the issue of executive privilege," Specter said. "The Senate has not asked for anything falling under executive privilege."

Specter also said the Judiciary Committee will look into a 1999 Dallas land condemnation deal in which Miers's family initially was granted 18 times the assessed value of a half-acre parcel needed for a freeway ramp. Knight-Ridder Newspapers reported Saturday that her family was awarded $106,915 for the property, after the state first had offered $5,900. A settlement reached in 2003 reduced the price to $80,915.

The panel that determined the price for the transaction was appointed by a Texas judge who had received at least $5,000 in campaign donations from the political action committee of Miers's law firm. Panel members have said the payment was fair.

"That's the sort of thing we'll have to look into," Specter told reporters yesterday.

As Miers faced intensifying opposition among conservatives, she continued preparing for her confirmation hearing, scheduled to begin Nov. 7. Miers also continued making the rounds on Capitol Hill, where she visited Sen. Tom Coburn (R-Okla.).

Several senators have expressed skepticism but none has announced plans to oppose her -- a point emphasized by her supporters. "There is not significant opposition in the U.S. Senate, and at the end of the day, they are the only ones who get to vote," said Jay Sekulow, chief counsel of the American Center for Law and Justice.

Sen. Lindsey O. Graham (R-S.C.) called the desire of some of Miers's critics for her to withdraw before her confirmation hearings "wishful thinking, not grounded by reality."

A coalition of conservative groups that includes the Eagle Forum, the Center for a Just Society and ConservativeHQ, have launched WithdrawMiers.org, as part of its effort to force Miers out. The site features articles critical of Miers, a box where readers can submit anonymous tips on her nomination and a petition calling for her to step down.

So far, several of the most politically potent conservative groups are either supporting Miers -- such as Focus on the Family, led by James C. Dobson -- or have stayed neutral with varying degrees of unease. Some groups in the latter category, such as the Family Research Council, are close to coming out formally against her, according to sources familiar with their internal deliberations.

Some skeptics say the longer Miers has been on stage since her Oct. 4 nomination, the more damage she has done to herself and Bush. Her answers to a Judiciary Committee questionnaire included a misinterpretation of constitutional law and were deemed so inadequate that the panel asked her to redo it. She revealed that her law licenses in D.C. and Texas had been temporarily suspended because of unpaid dues.

Addressing how Miers has been doing in her rounds of private meetings with senators, Graham said: "She comes across guarded. Some of the meetings have gone better than others. She is going to have to step it up a notch in terms of forcefully presenting why she should be on the Supreme Court. I think she is capable of that."

Her critics think otherwise. "At this point, that's the most politically appropriate move for President Bush or Miss Miers herself to make," said Jessica Echard of the Eagle Forum. "The nomination affirms the absurd policy that conservatives can only nominate these stealth nominees."

Conservative stalwarts David Frum, a former Bush speechwriter, and Linda Chavez, meanwhile, are among those supporting BetterJustice.com, another site seeking Miers's withdrawal. The group also has promised to launch radio and television ads to support their call.

"The sense is that she is not well versed in constitutional law. It is not to say she is not a good lawyer, a smart woman or had good careers," said Chavez, president of the Center for Equal Opportunity, which opposes race-conscious affirmative action programs. "But she is not someone who has spent time in the world of ideas."

Mark Smith, vice president of the New York chapter of the Federalist Society, who attended the Roberts swearing-in at the White House just last month, said Miers does not even deserve hearings. "If Miss Miers were truly a conservative, she would withdraw her nomination," he said. It is "certainly harming the Republican Party and the conservative movement," and she should pull out "if for no other reason than the good of the cause."

Staff writers Peter Baker and Amy Goldstein contributed to this report.

White House counsel Harriet Miers arrives on Capitol Hill for a meeting with Sen. Tom Coburn (R-Okla.) to discuss her nomination to the Supreme Court.