Over 43 years in the senate, Democrat Ted Kennedy has fought serial battles on behalf of the working class—from defending overtime pay and workplace-safety regulations to expanding health-care availability and penalizing discrimination. But the key to his legacy is not that he is determined to stick up for his principles. It's that he is willing to compromise on them.

Late in 1990, for example, Kennedy sat red-faced as House Democrat Pat Schroeder berated him for supporting something he didn't believe in: caps on damages for workplace discrimination. But by agreeing to limits, Kennedy won over the handful of Republican and Southern Democratic Senators he needed to secure passage of the Civil Rights Act of 1991, strengthening laws that banned job discrimination. The result was a law that protects women from sexual harassment at work and has yielded a surge in lawsuits and tens of millions of dollars in damages to aggrieved plaintiffs.

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"

Kennedy was a bit of a joke when he first arrived in Washington in 1962. When John F. Kennedy ran for President, he kept his Massachusetts Senate seat warm for his youngest sibling, placing a college buddy in it for two years until Teddy reached the constitutionally required age of 30. But starting with a 1965 bill that did away with country-by-country quotas for immigrants, and especially in the quarter-century since his failed 1980 campaign for President, Kennedy, 74, has amassed a titanic record of legislation affecting the lives of virtually every man, woman and child in the country. With a succession of Republicans, he helped create COBRA, the Americans with Disabilities Act, portable health care, the Family and Medical Leave Act and more than 15 key education programs, including the landmark 1965 Elementary and Secondary Education Act. He also pushed through the deregulation of the airline and trucking industries and the reduction of the voting age to 18. By the late '90s, the liberal icon had become such a prodigious cross-aisle dealer that Republican leaders began pressuring party colleagues not to sponsor bills with him.

Some bipartisan efforts have backfired on Kennedy. He has complained that he was taken in by Bush on the No Child Left Behind law because it was inadequately funded, and Democrats are distressed that he has collaborated with Republicans on immigration reform. Worse than that, critics say, Kennedy's inability to stop the confirmation of Supreme Court Chief Justice John Roberts and Justice Samuel Alito show he's losing his swat. But Kennedy still finds a way to deliver the goods for the less advantaged. Over the next five years, more than 100,000 severely disabled children will become beneficiaries of a new $872 million program that continues government health-care payments to them even as they move out of poverty. Kennedy and Iowa Republican Chuck Grassley managed to slip the program into last year's budget.