The last GOP presidential win in IL was Bush in 1988. Dukakis only had a margin of 250 K in Cook and that was not enough to carry him statewide as he lost by 100 K, even though there were still a lot of southern IL counties voting D.
Clinton had a 640 K margin in Cook in 1992 and that was most of his margin on 720 K that year. 1996 was similar with a 690 K margin in Cook and 750 K statewide. During this decade the inner townships of Cook really started to tilt D creating margins that were previously associated with statewide landslides.
In the 2000 election the tilt of downstate to R began to show. Gore carried Cook by 750 K but only won the state by 570 K. The difference downstate grows in 2004 as Kerry takes Cook by 840 K but only has a 550 K win statewide.
Obama clearly gets a favorite son effect, but it's instructive to compare 1992 to 2008. The shift of southern IL vs suburban Chicago is quite marked. Since Chicago and suburbs controls an ever larger fraction of the state's vote, the Cook county margins will continue to dominate the state.
what is downstate IL like? I'm guessing its kind of like rural Missouri?
Northern Illinois is more like Minnesota/Wisconsin/eastern Iowa, Southern Illinois is more like rural Missouri or Western Kentucky.
Western KY is a pretty good match to southern IL. The land and speech is similar. A lot of the area is old coal country. From the US Energy Information Agency: In 2010, Illinois ranked third in recoverable coal reserves at producing mines in the Nation; the state ranked eighth in production.
