[1] There is a significant division between Democratic-leaning cities and college towns, and highly conservative rural regions, which continue to be dominated by Republicans, but are drowned out due to their relatively low population.
Historically, Illinois was a critical swing state leaning marginally towards the Republican Party.
However, following Bill Clinton's election in 1992, and his victory in Illinois, the state has been realigned in favor of Democratic candidates for president, with eight consecutive wins by that party, regardless of the national outcome.
Traditionally, Chicago, East Saint Louis, and the Quad Cities region have tended to vote heavily Democratic, along with the Central Illinois population centers of Peoria, Champaign-Urbana and Decatur.
In recent years, Chicago's suburban collar counties continue to trend Democratic as well, contributing to the end of its swing state status, even as rural areas became even more heavily Republican.