Sen. Edward Kennedy, D-Mass., said that Mukasey's unwillingness to answer definitively on the legality of the interrogation method that simulates drowning increases chances that it could be used against U.S. troops.
"I therefore intend to oppose this nomination," Kennedy said in remarks prepared for the Senate floor. "Judge Mukasey appears to be a careful, conscientious and intelligent lawyer, and he has served our country honorably for many years. But those qualities are not enough for this critical position at this critical time."
On the upside for the administration, Republican Sens. John McCain of Arizona and Lindsey Graham of South Carolina, announced they would support Mr. Bush's nominee.
Mr. Bush said it was unfair to ask Mukasey about interrogation techniques on which he has not been briefed. "He doesn't know whether we use that technique or not," the president told a group of reporters invited into the Oval Office.
Further, Mr. Bush said, "It doesn't make any sense to tell an enemy what we're doing."
Sen. Chuck Schumer, D-N.Y., whose vote may decide whether Mukasey's nomination advances from the Judiciary Committee next Tuesday, said he has not decided but defended his fellow Democrats who have.
"I do not think Democrats are mistreating him at all," Schumer told reporters.
Prospects for Mukasey's confirmation have dimmed because of his refusal to equate waterboarding with torture. Four of the 10 Democrats on Judiciary have now said they'll vote against him.
In a potentially ominous sign for the administration, Majority Leader Harry Reid, D-Nev., told reporters he could not guarantee a floor vote if Mukasey's nomination fails in committee.
"I really believe in the committee process," said Reid, who has not announced how he would vote. "If I'm asked by members of the committee to stay out of the fray, I am willing to do that."
Reid also said it's perfectly appropriate to ask the attorney general nominee to clearly state his view on torture and acknowledge that a technique that began during the Spanish Inquisition qualifies.
"The chief legal officer of this country, the attorney general of the United States, shouldn't we know how he stands on waterboarding and torture generally?" asked Reid, D-Nev.
Reid said it's like the "twilight zone" to be told this shouldn't be discussed, CBS News correspondent Bob Fuss reports.