He enjoyed a good martini and a fast game of squash, and he was famous for parsing his words to wiggle out of tight spots. During Mr. Clinton’s impeachment on charges of perjury and obstruction, Mr. Specter, objecting to what he called a “sham trial” without witnesses, signaled that he would vote to acquit.

But a simple “not guilty” vote would have put him directly at odds with Republicans; instead, citing Scottish law, Mr. Specter voted “not proven,” adding, “therefore not guilty.”

He relished the decades he spent on the Judiciary Committee. He enraged conservatives in 1987 by helping to derail Judge Bork’s nomination to the Supreme Court and then delighted them four years later by backing Justice Thomas. The Thomas confirmation nearly cost Mr. Specter his Senate seat; even now, millions of American women remain furious with him for his aggressive questioning of Anita F. Hill, a law professor who had accused Justice Thomas of sexual harassment when they worked together at the Department of Education and the Equal Employment Opportunity Commission.

If he had any regrets, Mr. Specter rarely admitted them.

“I’ve gone back and looked at every frame of the videos on Professor Hill, and I did not ask her one unprofessional question,” he said in a 2004 interview with The New York Times. Of the Bork and Thomas confirmations, he said, “I may be wrong, but I’m satisfied with what I did in both those cases.”

Brash confidence and outsize ego were characteristic of Mr. Specter, a man so feared by his own aides and so brusque with colleagues that he earned the nickname Snarlin’ Arlen on Capitol Hill. In 1992, when Mr. Specter’s Senate seat was in danger after the Thomas hearings, Paul Weyrich, a founding father of the modern conservative movement, campaigned for him. His rationale was expressed in a statement he made to fellow conservatives, as quoted by the conservative magazine National Review.