The Chicago Tribune/WGNTV poll finds that 52-percent of Illinoisans surveyed backed Kerry, compared with 38-percent who favor Bush going into the November election.
The results are identical to a Tribune/WGN poll taken in February, before Kerry had even won his party's nomination.
Only five-percent of those polled said they're still undecided, while four- percent planned to vote for another candidate.
The survey also found that 42-percent of Illinois voters call themselves Democrats, compared to 29-percent who identify themselves as being Republican.
The survey of 700 likely voters in Illinois had an error margin of four percentage points.