A head to head comparison of the Illinois 2016 General Election gives us an idea of the break down of the voters.
Tammy Duckworth received 3M (54.9 %) votes, beating Mark S. Kirk who gained 2.2M (39.8 %) by 828.2k votes in Illinois.
Tammy Duckworth won 17 counties out of the 102 counties that make up Illinois. The record shows that Mark S. Kirk won 85 counties.
During the 2016 general elections, over 5M total number of votes were cast. Kenton McMillen got 175,988 (176k) over Mark S. Kirk 2,184,692 (2M). He won the popular vote by 175,988 (176k). His victory in the State of Illinois (with 175,988 votes) represents 50.0% of his popular vote victory.
Top 15 Counties in General Elections
All Candidates (Senate General Elections)
These 15 counties play an important role in these Primary elections. If a candidate, can get a sizable majority in the largest counties (Cook, DuPage and Will), it becomes very difficult to win majorities in the smaller counties without voter outreach and increased voter participation in them.
Top 15 Counties Comparison in General Elections
Mark S. Kirk
Cook, DuPage and Will, three of the larger counties voted in favor of Tammy Duckworth, giving him a 1M vote advantage.