The election was very close. Simon prevailed by only 89,126 votes, or 1.86%. Incumbent Percy did well throughout the state, including the Chicago collar counties. However, in the heavily populated and DemocraticCook County, which encompasses the city of Chicago and the majority of the Chicago Metropolitan Area, Simon ran ahead of Percy by over 300,000 votes. Simon also won most counties in southwestern Illinois, a traditionally Democratic region. Percy led early on and well into the night, but as Cook County began to count all of its votes, Simon pulled ahead. Simon won despite then-president Reagan winning the state easily. Percy called Simon at around 5 A.M. the next day and conceded. Percy also congratulated Simon on his hard-earned victory. Simon was sworn in on January 3, 1985, and served in the senate until January 3, 1997, when he retired. Simon was later succeeded by Dick Durbin, a close friend and fellow Democrat.
United States Senate election in Illinois, 1984