The Chicago Tribune/WGN TV poll found 49 percent of Illinois voters say they're backing Kerry, while 40 percent say they'll vote for Bush. A similar poll a month ago showed Kerry leading Bush 52 percent to 38 percent.
The latest poll shows the number of undecided voters has doubled from five percent to 10 percent.
The survey of 700 registered voters was conducted Sept. 17 through Sept. 20. It has an error margin of four percentage points.