CARBONDALE, Ill. (AP) _ Former Sen. Paul Simon was honored Sunday in a memorial service filled with dignitaries who paid tribute to the popular, low-key senator as a tireless advocate for the oppressed.

Simon's plain casket _ topped by the art work of his grandchildren _ rested in front of a stage at Southern Illinois University's sports arena, where more than 3,500 people attended a service that included a 60-piece orchestra.

Massachusetts Sen. Ted Kennedy compared Simon to his brother Robert Kennedy.

``Paul Simon had that quality of moral courage in abundance,'' Kennedy said from the flower-covered stage.

``He couldn't have cared less about the games of politics; that's why he was successful in politics,'' Kennedy said.

Bill Clinton, originally scheduled to speak, sent his regrets after bad weather grounded his plane.

Mourners at the service included Illinois Sen. Dick Durbin, former Wyoming Sen. Alan Simpson, Chicago Mayor Richard M. Daley and former U.S. Labor Secretary Lynn Martin.

Illinois Gov. Rod Blagojevich linked Simon to Illinois, where the son of Lutheran missionaries first moved as a 19-year-old.

``He may have been born in Oregon, but he was raised on the values of the heartland of Illinois,'' Blagojevich said.

Simon, 75, died unexpectedly Dec. 9 in Springfield after suffering complications from heart surgery.

He told his family years ago he wanted a low-key church funeral that didn't focus on him too much. Instead, mourners at the musical, prayerful and emotional service hailed him as a friend of people in need and a decent man even to his adversaries.

When Republican Sen. Jesse Helms once opposed a judicial candidate Simon endorsed, Simon irked his Democratic colleagues by lecturing them on the conservative's good qualities, said former federal judge Abner Mikva, the only speaker Sunday who Simon had specifically requested to speak at his funeral.

``He never missed an opportunity to support his causes,'' Mikva said, even in the final days of his life, as he touted Democratic presidential contender Howard Dean from his Springfield hospital bed, Mikva said.

Simon's son, Martin, 39, spoke in a trembling voice about how his dad raised him with a soft hand and firm principles.

``He didn't teach me to be a good person, he showed me,'' Martin Simon said.

Simon will share a tombstone with his wife of 40 years, Jeanne, who died in 2000.

Survivors include his wife of two years, Patricia Derge Simon of Carbondale, his daughter, Sheila Simon of Carbondale, Martin Simon of Crofton, Md., and four grandchildren.