If you need visual proof of the political differences between the Chicago area and most of downstate Illinois, just look at the recent gubernatorial election.
JB Pritzker gained the support of the more populated Cook and collar counties. But elsewhere, there were only a few patches of blue, surrounded by deep red. Still, Pritzker had more than enough support to win statewide.
While Democrats have been able to claim victory at the state level and pass more progressive laws, there is growing dissatisfaction in areas Republicans represent. Several counties have even gone on record supporting secession from Illinois.