A day after undergoing heart surgery, former Sen. Paul Simon (D-Ill.) died today at 75.

Doctors performed single bypass heart valve surgery at St. John’s Hospital in Springfield, Ill., on Monday. Simon was in the hospital when he passed away.

The bow-tie-wearing Senator, who is fondly remembered for being impersonated by Al Franken on “Saturday Night Live,” served five terms in the House, two terms in the Senate and ran for the Democratic presidential nomination in 1988.

Terry Michael, the executive director of the Washington Center for Politics and Journalism who was a longtime friend of Simon’s said his death came as a “shock.” Michael said he will fondly remember his friend as “a rare politician whose respect came because he understated his arguments in an era in which politics became about verbal food fights. … He understood that you gain respect not by raising your voice but by raising good arguments.”

During his time on Capitol Hill, Simon was one of the key advocates for a balanced-budget amendment, education policies and curbing entertainment violence. He was also the chief sponsor of the National Literacy Act.

Although Simon’s political career spanned more than four decades, he was often thought of as the quiet man in glasses who became known as a relentless legislator. He was first elected to the Illinois House of Representatives in 1955. He served throughout the 1950s, ’60s and early ’70s in the state Senate and as the Prairie State’s lieutenant governor before winning a bid for the House in 1974. He moved to the Senate in 1984 and retired 12 years later.

Simon, one of the most liberal Members of the Senate during his years of service, once said he fell into his political career quite by accident — after uncovering corruption in his hometown through his job as an investigative reporter.

The tough Senator also enjoyed showing his sense of humor. Once, when Paul Simon was slated to host “Saturday Night Live,” both the Senator and the musician walked on stage and proceeded to have a mock argument about which one was going to be the host of the show.

Since his retirement from politics, Simon turned to education and became director of the Public Policy Institute at Southern Illinois University.

“Paul Simon was one of the finest public servants that I have been privileged to know. He brought a unique passion and integrity to his work in the Senate,” said Sen. Robert Byrd (D-W.Va.) “Senator Simon served his country as a journalist, newspaper editor, businessman, soldier, teacher, and legislator. In each of these endeavors, he always displayed the highest level of skill, integrity, and honesty that serves as an example for all Americans. I will always have a tremendous respect for Paul Simon.”

Simon is survived by his daughter, Sheala, and son, Martin.