A conservative group opposing Harriet Miers (search) bought $250,000 of television and radio time Tuesday to broadcast an advertisement nationwide calling for President Bush to withdraw his nominee for the Supreme Court.

The White House said it was standing behind Miers. "She is going to be going before the Senate Judiciary Committee in less than two weeks," Bush spokesman Scott McClellan (search) said. "She looks forward to answering their questions. And I think that people should not try to rush to judgment on it."

The ad by Americans for Better Justice is the first anti-Miers television spot and is evidence of the battle the White House is facing over her nomination. A relatively small purchase, it will air nationally for a week on FOX News Channel.

Bush named Miers, 60, about a month ago to succeed retiring Justice Sandra Day O'Connor (search), a swing vote on the court's abortion and affirmative action decisions. The conservative group Progress for America Voter Fund (search) supported her nomination with television ads.

But many conservatives have criticized the president for nominating someone with no experience as a judge and a scant public record on issues such as abortion rights.

"Conservatives have worked too hard for too long to settle for anything less than our very best on the Supreme Court," said David Frum, a former Bush speechwriter who serves as a spokesman for Americans for Better Justice.

Miers, Bush's legal counsel, worked on gaining Senate support on Tuesday, scheduling visits with Republicans John Ensign of Nevada and Johnny Isaakson of Georgia, and one committee member, Sen. Russ Feingold, D-Wis. Miers' guide through the confirmation process, former GOP Sen. Dan Coats of Indiana, spoke to the Senate Republicans' weekly policy luncheon.

None of the Senate's 55 Republican senators publicly has opposed Miers. Sen. John Thune, R-S.D., among those who have said conservatives would have preferred a different nominee, said he expects most Senate Republicans to stay silent on Miers until the hearings that are set to begin Nov. 7.

"I think most people are granting her, according her, the benefit of the doubt, subject to the time she has to appear before the committee to make her case in person," Thune said.

Committee aides have begun interviewing participants on an Oct. 3 conference call in which two of Miers' longtime friends said they believed she would vote to overturn Roe v. Wade (search), the 1973 ruling that established abortion rights.

Gary Bauer, president of American Values, met with four committee lawyers on Monday, said his spokeswoman, Kristi Hamrick. She said Bauer told the lawyers that he asked Texas Supreme Court Judge Nathan Hecht and U.S. District Court Judge Ed Kinkeade (search) during the call whether their comments were authorized by the White House (search) or Miers. Bauer said the judges said they were offering personal opinions, not authorized assurances, she said.

Committee lawyers hope to interview Hecht and Kinkeade, as well as James Dobson, head of Focus on the Family. He said he received private assurances from the White House that Miers is opposed to abortion.

Dobson has told the committee's top Republican aide he had not received information on how Miers might rule on Roe, spokesman Paul Hetrick said.

Senators are negotiating with the White House over what kind of documents the administration will release from Miers' work for Bush. Bush has said he will not turn over documents detailing the private advice Miers gave him while serving in the White House, but senators say the administration has documents that can be shared without interfering with the president's ability to get advice.

"I think we can get materials which will be helpful to us," said the committee's chairman, Sen. Arlen Specter, R-Pa.

Miers was expected on Wednesday to give the Senate her answers to a second questionnaire from the committee. Specter and the committee's top Democrat, Vermont Sen. Patrick Leahy (search), criticized Miers' responses to the committee's first questionnaire as vague and incomplete.

"I would hope they would be a lot more complete than last time," Leahy said.