Washington ? A conservative group opposing Supreme Court nominee Harriet Miers bought $250,000 of TV and radio time Tuesday to broadcast an advertisement nationwide calling for President Bush to withdraw her nomination.

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 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 ad, and it demonstrates the ongoing 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 about a month ago as the replacement for retiring Justice Sandra Day O’Connor, a swing vote on the court’s abortion and affirmative action decisions. The conservative group Progress for America Voter Fund supported her nomination with television ads.