WASHINGTON — President Bush delivered a vigorous defense Thursday of his embattled attorney general nominee Michael Mukasey, charging that Senate foes are holding the former judge to an impossible standard, one no nominee could meet.

Many Senate Democrats are turning against Mukasey because he told the Senate Judiciary Committee that he considers a controversial interrogation technique known as waterboarding "repugnant," but he wasn't certain that it was illegal. Many Democrats and civil libertarians believe that waterboarding — in which a captive is strapped to a board, a cloth is placed over his mouth and water is poured over it to simulate drowning — is torture, illegal, unethical and ineffective.

If the Senate rejects Mukasey because of his stand on waterboarding, Bush said, "they would set a new standard for confirmation that could not be met by any responsible nominee for attorney general and that would guarantee that America would have no attorney general during this time of war."

Actually, America has an acting attorney general in charge of the Justice Department right now — Peter D. Keisler — whom Bush appointed in September after Attorney General Alberto Gonzales resigned. Keisler, a Yale Law graduate and veteran Washington attorney, has served in senior Justice Department positions since 2002. He'll remain in office until a successor is confirmed.

Bush inserted his Mukasey defense into a speech on terrorism before the Heritage Foundation, a conservative research group on Capitol Hill. A few blocks away, he lost a crucial vote as Sen. Edward M. Kennedy, D-Mass., said in a Senate floor speech that he would oppose Mukasey because his "extreme views" are "not only immoral but legally flawed." Kennedy sits on the judiciary committee.

Bush contended that Mukasey has answered senators' questions thoroughly and as well as he possibly could.

"As the price for his confirmation," the president said, "some on that (Senate Judiciary) committee want Judge Mukasey to take a legal position on specific techniques allegedly used to interrogate captured terrorists."

Mukasey can't do that for at least three reasons, Bush said:

— He doesn't know whether such methods are used, since the information is classified.

&mdash He doesn't want to offer an opinion that could put U.S. interrogators in legal jeopardy.

&mdash And he "does not want any statement of his to give the terrorists a window into which techniques we may use and which ones we may not use."

Such information, Bush said, "could help them train their operatives to resist questioning and withhold vital information we need to stop attacks and save lives."

The Senate Judiciary Committee is expected to vote on Mukasey on Tuesday. It includes 10 Democrats and nine Republicans, so it will probably take only one Democratic vote for Mukasey to send the nomination to the full Senate.

Republicans are rallying behind him; on Thursday, Sen. Lindsey Graham, R-S.C., a committee member, said he would vote yes. Sen. John McCain, R-Ariz., who's influential on questions of torture as a former Vietnam prisoner of war, also endorsed him.

The key committee vote could come from Sen. Charles E. Schumer, D-N.Y., who praised Mukasey before the controversy erupted, but hasn't said how he'll vote. Sen. Dianne Feinstein, D-Calif., is also considered a key vote; she hasn't declared her intention.

Kennedy, the second-ranking judiciary Democrat, joined three other committee members, including Majority Whip Richard Durbin, D-Ill., in opposing Mukasey.

"Waterboarding is torture. Period," Kennedy said. "Yet Judge Mukasey refuses to say so."

(Marisa Taylor contributed.)