Washington ? President Bush on Thursday raised the stakes in his contest with Senate Democrats over the nomination of Michael B. Mukasey as attorney general, saying they were subjecting the nominee to a unique and unfair standard and could cause the Justice Department to be left without leadership at a critical juncture.

Bush, in his most forceful remarks to date on the troubled nomination, strongly defended Mukasey for refusing to say whether he believed that a coercive interrogation technique known as water-boarding was illegal torture. The issue has become the defining question for Senate Democrats in advance of Tuesday’s Senate Judiciary Committee vote on whether to confirm the retired federal judge to succeed Alberto R. Gonzales.

“If the Senate Judiciary Committee were to block Judge Mukasey on these grounds, they would set a new standard for confirmation that could not be met by any responsible nominee for attorney general,” Bush said. “And that would guarantee that America would have no attorney general during this time of war.”

Mukasey has declined to offer an opinion on the legality of interrogation methods, saying he has not been briefed on what programs the administration is using. He has also said he does not want to make an uninformed judgment that could tip off terror suspects or expose American interrogators to legal action.

“It’s wrong for congressional leaders to make Judge Mukasey’s confirmation dependent on his willingness to go on the record about the details of a classified program,” Bush said in a speech to the Heritage Foundation, a conservative think tank, in Washington.

Bush’s declaration appeared to do little to stem growing Democratic opposition to the nominee. On Thursday, Sen. Edward M. Kennedy, D-Mass., became the fourth Democrat on the judiciary committee to declare his opposition to Mukasey.

The panel’s chairman, Sen. Patrick Leahy, D-Vt., is expected to announce his position at a briefing in his home state today. Most observers believe that Leahy will oppose the nominee, although his office declined comment in advance of the briefing.

Bush’s comments on Thursday raised the question whether he would nominate anyone else to succeed Gonzales should the Senate reject Mukasey. The Justice Department is currently run by an acting attorney general, Peter Keisler, who had announced plans to leave the department until Bush prevailed upon him to serve as a temporary steward in the wake of Gonzales’ departure in mid-September.

There was also speculation that Bush might use a recess appointment to install Mukasey at the department during the congressional holiday break. That would enable Mukasey to serve unconfirmed until a new Congress convenes, and Bush leaves office, in January 2009.

But congressional sources said they doubted Majority Leader Sen. Harry Reid. D-Nev., would stand for such a maneuver, and would try to outflank Bush by keeping some lawmakers in Washington over the break to ensure that the chamber was always in session.

Dana Perino, the White House press secretary, was asked Thursday if Bush was saying he would not put forward any other nominee if Mukasey were rejected. “We don’t believe it would come to that,” she said. “No nominee could meet the test they’ve presented.”

Most observers believe that Mukasey would be confirmed if his nomination were voted upon by the full Senate. But Reid appears unlikely to allow a floor vote if the judiciary committee rejects the nomination.

There is precedent for the committee to forward a nomination to the full Senate without a recommendation or with a negative recommendation. Leahy has indicated that he has no plans to permit that, but the idea could be raised by other lawmakers as a compromise.