Washington ? The chairman of the Senate Judiciary Committee served notice Wednesday he intends to question Harriet Miers about the Bush administration’s policy of detaining suspected terrorists at Guantanamo Bay, injecting new uncertainty into a Supreme Court nomination already in doubt.

In a letter to Miers, who is White House counsel, Sen. Arlen Specter also said he would ask what assurances she could offer that she would be independent, if confirmed, “and not give President Bush any special deference on any matter involving him that might come before the court.”

Specter, R-Pa., released the letter as the White House struggled to build support for an appointment that has drawn withering criticism from some prominent conservatives outside Congress and steady skepticism – or worse – from Republican senators.

Three GOP officials said they no longer felt certain that Miers’ troubled nomination would survive as long as the Nov. 7 target date for hearings, and that a withdrawal was not out of the question. They spoke on condition of anonymity, noting that the administration’s official policy is one of strong continued support for the president’s pick.

Miers met with Sen. David Vitter, R-La., the latest in a round of senatorial courtesy calls, and labored to answer written questions from the Judiciary Committee by day’s end. The panel sought the information after deeming her earlier responses incomplete.

Vitter declined to tell reporters what Miers had told him about the speech she made a dozen years ago. Sen. Sam Brownback, R-Kan., said it raised another question in his mind about her views. “It’s something we’ll have to probe,” he said.