Centrist Sen. Specter Died Fighting for Moderation Arlen Specter, a pugnacious and prominent former moderate in the U.S. Senate who developed the single-bullet theory in President John F. Kennedy's assassination and played starring roles in Supreme Court confirmation hearings, lost a battle with non-Hodgkin lymphoma at a time when Congress is more politically polarized than anyone serving there - or living in America - can remember. Specter, 82, died Sunday, after spending much of his career in the U.S. Senate warning of the dangers of political intolerance. President Barack Obama ordered U.S. flags at the White House and other public buildings flown at half-staff Tuesday, the day of Specter's funeral. For most of his 30 years as Pennsylvania's longest-serving U.S. senator, Specter was a Republican, though often at odds with the GOP leadership. He drew the lasting ire of conservatives by helping end the Supreme Court hopes of former federal appeals Judge Robert H. Bork and the anger of women over his aggressive questioning of Anita Hill, a law professor who had accused Supreme Court nominee Clarence Thomas of sexual harassment. He even mounted a short-lived run for president in 1995 on a platform that warned his fellow Republicans of the "intolerant right." FILE - In this Monday, March 29, 2010, file photo, Sen. Arlen Specter, D-Pa., leads a Senate field hearing, in Philadelphia. (AP Photo/Matt Rourke, File) Close Specter never had his name on a piece of landmark legislation. But he involved himself deeply in the affairs that mattered most to him, whether trying to advance Middle East peace talks or federal funding for embryonic stem cell research. He provided key votes for President Barack Obama's signature accomplishments, the health care and economic stimulus bills. Specter died at his home in Philadelphia from complications of non-Hodgkin lymphoma, said his son Shanin. For over three decades, I watched his political courage accomplish great feats and was awed by his physical courage to never give up. Arlen never walked away from his principles and was at his best when they were challenged," said Vice President Joe Biden, with whom Specter often rode the train home from Washington, D.C., when Biden also served in the Senate. Said former Pennsylvania Gov. Ed Rendell, "Arlen wanted to die in the Senate, and in many ways he should have." On Monday, Republican Gov. Tom Corbett ordered Pennsylvania flags at the Capitol and all other commonwealth facilities lowered to half-staff until sundown Tuesday. Intellectual and stubborn, "snarlin' Arlen" took the lead on a wide spectrum of issues and was no stranger to controversy. He rose to prominence in the 1960s as an assistant district attorney in Philadelphia prosecuting Teamsters officials for conspiracy to misuse union dues and as counsel to the Warren Commission, where he developed the "single-bullet fact" in Kennedy's assassination, as he called it. He came to the Senate in the Reagan landslide of 1980 and, as one of the Senate's sharpest legal minds, took part in 14 Supreme Court confirmation hearings.