WASHINGTON -- The lights went out yesterday on Sen. Arlen Specter's chairmanship of the Senate Judiciary Committee -- literally.

A five-minute power outage temporarily halted the Pennsylvania Republican's tough questioning of FBI Director Robert Mueller during one of the committee's last meetings before Democrats take control of both houses of Congress.

In January, Mr. Specter will pass his gavel to Sen. Patrick Leahy, D-Vt.

"I yield," he said as aides fidgeted with the lights, prompting an uproar of laughter from Mr. Leahy and the sizable crowd in the wood-paneled meeting room.

A final judiciary hearing is scheduled for today.

It has been an eventful two years at the helm of one of the Senate's most powerful committees. Mr. Specter has overseen confirmation of two additions to the Supreme Court -- Chief Justices John G. Roberts Jr. and Justice Samuel A. Alito Jr.

Mr. Specter also has worked on renewal of the Civil Rights Act and legislation connected to President Bush's controversial domestic wiretapping program for monitoring terrorist activities. That legislation is unlikely to move forward in the wake of the Republicans' election defeat last month.

Yet Mr. Specter, unwilling to waste his remaining time as chairman, put the issue at the center of yesterday's meeting. He complained that, to date, no one from the Bush administration had briefed his panel on the specifics of wiretapping efforts, which were revealed in December 2005 by The New York Times.

"What assurances can you provide this committee and the American people that the program is worthwhile?" Mr. Specter asked Mr. Mueller. "Have arrests been made? Have terrorist cells been broken up?"

"I'm not going to be able to satisfy you here," Mr. Mueller replied. He said he didn't have permission to discuss details, although FBI and CIA officials had already briefed the Senate Intelligence Committee.

That didn't sit well with Mr. Specter. "I'm not too anxious to hear that you report to the Intelligence Committee," he said. "I am anxious to hear that you report to this committee. Because this committee has oversight jurisdiction over the FBI."

He also pushed Mr. Mueller about whether the FBI has been properly reviewing its activities under the Patriot Act, another controversial law that grew out of the Sept. 11, 2001, terrorist attacks. When the director responded that the Department of Justice was responsible for releasing the information, Mr. Specter scoffed.

"Is your coordination with the CIA as good as your coordination with the Department of Justice?" he asked, hinting at the tense relationship and communication problems between two agencies on the front lines of the war on terror.

"They're both equally good, Mr. Chairman," Mr. Mueller said.

"Equally good and equally bad," Mr. Specter replied.

Mr. Specter also signaled this week that he'll join prominent Democrats in seeking to restore legal rights to hundreds of suspected terrorists held in the U.S. military prison at Guantanamo Bay, Cuba, and elsewhere.

While the measure to restore the right of habeas corpus has almost no chance of passing before Congress adjourns later this week, the message is clear: When Democrats take over next month, the issue could resurface.

The Military Commissions Act of 2006, which Mr. Bush signed into law in October, prevents detainees who aren't U.S. citizens from challenging their detentions in civilian courts. But Mr. Specter, who voted for the legislation despite his opposition to stripping such rights from detainees, yesterday reintroduced legislation to restore those rights. A similar measure he sponsored failed by three votes in October.

In a Senate floor speech, Mr. Specter said he was reintroducing the issue to prevent federal courts from striking down the act, which some detainees' attorneys have challenged.

But some lawmakers privately speculated that Mr. Specter may have decided to reintroduce the legislation after a recent New Yorker magazine article suggested that his desire to retain his powerful chairmanship had led him to accede to administration wishes.

Mr. Specter yesterday repeated his contention that "the Constitution of the United States is explicit that habeas corpus may be suspended only in time of rebellion or invasion. We are suffering neither of those alternatives at the present time," he said on the Senate floor. "We have not been invaded, and there has not been a rebellion."

Now in his fifth term, the 76-year-old former prosecutor has long been known for his hard-hitting inquiries and a willingness to buck his party leaders. The chairmanship was a prized acquisition when he won re-election two years ago.

In recent years, the GOP's steady drift to the right has constrained Mr. Specter, one of the few remaining Senate moderates. Soon after his 2004 victory, he enraged conservatives by suggesting that a Supreme Court nominee who opposed abortion rights would face likely defeat in the Senate. That opinion nearly cost him his gavel, but Mr. Specter staved off his critics with key promises to Republican colleagues.

"I have assured the president that I would give his nominees quick committee hearings and early committee votes, so floor action could be promptly scheduled," he said in November 2004. "I have no reason to believe that I'll be unable to support any individual President Bush finds worthy of nomination."

Indeed, Mr. Specter kept his word, shepherding Mr. Roberts and Mr. Alito through his committee without much of the rancor from earlier hearings on Supreme Court nominees.

This week, however, his committee declined to take up a series of lower-court nominations that have irked Democrats. Yesterday, he cautioned the Bush administration against engaging in partisan battles with the new Democratic majority over judges. "Let's figure out who we can agree on, so we don't spin our wheels," he said.

He praised incoming Chairman Leahy, noting a strong relationship with the Vermont Democrat. Still, he said he hoped to be back at the top of the committee within a few years.

"I'm going to be sorry to lose the gavel," Mr. Specter said.