Rep. Paul Simon (D-Ill.), 55, a man of strong principles but gentlemanly ways from Illinois' southernmost "Little Egypt" district, defeated three-term Sen. Charles H. Percy (R-Ill.) Tuesday.

The five-term congressman forced the chairman of the prestigious Senate Foreign Relations Committee on the defensive, from personal income taxes to votes for arms sales to Arab countries.

With his low-key style and high-flown reformer's rhetoric, accentuated by an ever-present bow tie, Simon looks like an Everyman edition of the preacher's son -- which is what he is.

Simon was born Nov. 29, 1928, in Eugene, Ore., and moved to Illinois as a young man. At 19, he bought his own newspaper, the Troy Tribune, becoming the nation's youngest editor-publisher.

He earned a reputation as an independent-minded, unswerving advocate of civil rights, federal aid to education and the needy, and the causes of organized labor.

All this in a region closer geographically and emotionally to Jackson, Miss., than to Chicago.

Simon spent 14 years in the Illinois legislature and ran for lieutenant governor in 1969, proving to be one of the most popular vote-getters in state history.

After a bid for the governorship foundered in a primary loss in 1972, Simon took a two-year vacation from politics, then ran for the House in 1974. He has won ever since.

A moderate liberal, Simon has a special interest in education and served on the House Education and Labor Committee. He said at a victory news conference in Chicago yesterday that he would seek a seat on the Senate Labor and Human Resources Committee.

He also said he wanted to focus on unemployment and hoped to draw business and education leaders into efforts to stimulate high-technology industry to help replace the state's Rust Belt industries.

He, his wife, Jeanne, and their two children are known for enjoying the rigors of campaigning