“I don’t know what is involved in the technique,” Mr. Mukasey replied. “If waterboarding is torture, torture is not constitutional.”

Mr. Whitehouse described Mr. Mukasey’s response as a “massive hedge” since the nominee refused to be drawn into a conversation about whether waterboarding amounted to torture; many lawmakers from both parties, as well as civil liberties and human rights groups, have said that it is clearly a form of torture. The Bush administration has suggested that it ended the practice after protests from Capitol Hill and elsewhere, although it has never said so explicitly.

“I mean, either it is or it isn’t,” Mr. Whitehouse continued. Waterboarding, he said, “is the practice of putting somebody in a reclining position, strapping them down, putting cloth over their faces and pouring water over the cloth to simulate the feeling of drowning — is that constitutional?”

Mr. Mukasey again demurred: “If it amounts to torture, it is not constitutional.”

Mr. Whitehouse said he was “very disappointed in that answer — I think it is purely semantic.”

“I’m sorry,” Mr. Mukasey replied.

While Mr. Mukasey still seemed almost certain to win Senate confirmation, a vote in the Judiciary Committee could be delayed until Mr. Mukasey provides written answers to questions raised today by Mr. Leahy. The senator said he did not intend to hold the vote until after the responses were received and reviewed.

The committee’s ranking Republican, Senator Arlen Specter of Pennsylvania, said today that while he shared some of Democrats’ concerns about Mr. Mukasey’s views on the limits of presidential authority, “I think you are virtually certain to be confirmed, and we’re glad to see the appointment and glad to see somebody who is strong, with a strong record, take over this department.”

Other Republicans joined in the praise of Mr. Mukasey. “I’ve listened to your testimony here, and it seems to me that you are extraordinarily well-suited for this position, as pretty much as well as anybody who hasn’t served in the position before could be.,” said Senator Jon Kyl, Republican of Arizona.