The Sun Times has some poll numbers.
"Kerry leads Bush 48 percent to 43 percent among likely Illinois voters, but Kerry's margin narrowed considerably from a March 3 poll when he outscored the president by 13 points. At that time, focus on the Democratic presidential nomination created a Bush-bashing environment."
-- As others have pointed out, the media spending point is not really relevant since neither side is really spending on media in Illinois (at least Chicago) like they are in 'battleground' states.
However is this close enough to put the state in-play. We shall see,