Plenty of people succeed in politics by being everyone's friend. It takes a special talent to make it as a guy whom allies call "abrasive," "brutal" and "prosecutorial." Republican Arlen Specter of Pennsylvania is known for being blunt, not sparing even members of his own party. Unsatisfied with answers Attorney General Alberto Gonzales gave in hearings on the Administration's no-warrant domestic-wiretapping last February, he said the AG's defense "defies logic and plain English," and told the Washington Post Gonzales was smoking Dutch Cleanser. And although Specter has mellowed in recent years, his recent brush with mortality (he's fighting Hodgkin's disease) has made his famous impatience more acute. No wonder few Republicans will accept invitations to join him on foreign trips, even when they are to South America and the Middle East.

America's Best Senators Those who do, and don't, make a difference in the U.S. Senate The Best Senators Thad Cochran Kent Conrad Dick Durbin Ted Kennedy Jon Kyl Carl Levin Richard Lugar John McCain Olympia J. Snowe Arlen Specter The Worst Senators Daniel Akaka Wayne Allard Jim Bunning Conrad Burns Mark Dayton From the TIME Archive Nov. 5, 1979 The Kennedy Challenge More than a quarter century ago, TIME covered the presidential campaign of Senator Ted Kennedy, "the last of the Kennedy brothers, the youngest, the most vulnerable, the most thoroughly political"

The chairman of the formidable Judiciary Committee is an equal-opportunity offender. He nearly lost his 1992 Senate race when feminists mobilized against him after he grilled witness Anita Hill during the Supreme Court nomination hearings of Clarence Thomas. In 2004 Specter found himself on the other side of the feminist divide, nearly losing his long-awaited chance to run the committee when he opined that a Supreme Court nominee opposed to abortion rights wouldn't make it through the Senate.

Specter's principled contrarianism fits in the tradition of lawmakers Senate historian Richard Baker describes as the conscience of the institution, men and women who "stand up and say, 'Hold on a minute.'" In addition to conducting hearings on Bush's no-warrant wiretap program, Specter, 76, has repeatedly challenged FBI chief Robert Mueller on what he sees as shortcomings in the agency's performance; he chided the Justice Department for not participating in hearings on protecting reporters' sources and sent the White House a blistering list of questions he would have asked Harriet Miers had she not withdrawn from consideration as a Supreme Court Justice.

Specter can also be constructive. With Patrick Leahy, the ranking Democrat on the Judiciary Committee, he turned what could have been colossal battles over the Supreme Court nominations of John Roberts and Samuel Alito into disciplined and respectful hearings. He has hammered out enormously complex deals in committee on asbestos compensation and immigration reform. And as chairman of a powerful appropriations subcommittee, he was largely responsible for doubling spending on the National Institutes of Health and for increasing education spending 146% over 11 years. All of which he's managed while surviving a brain tumor, open-heart surgery and, in the past year, the chemotherapy treatment for his Hodgkin's disease. Says his former chief of staff David Urban: "You can find a lot of people who don't like Arlen Specter, but you can't find anyone who doesn't respect him."