If by some chance Roland Burris was able to win the Democratic nomination for a full Senate term next year, the seat would likely go Republican. Mark Kirk leads him 53-19 in a hypothetical contest.
Burris' approval rating is just 17%, easily the lowest PPP has ever registered for any politician. In the contest against Kirk he gets just 34% even of the Democratic vote and trails 62-8 among independents.
It looks like Kirk has some potential to be competitive even if Burris is not the nominee though. He is tied 35-35 with Alexi Giannoulias in a hypothetical contest and leads Jan Schakowsky 37-33.
Those numbers are a little optimistic for Republicans because in each of those contests more than 30% of Democrats but fewer than 20% of GOP voters are undecided. That is likely a function of the uncertainly about what will happen with this seat next year from the Democrats' end and as that gap closes both Giannoulias and Schakowsky would lead Kirk. He would still be in striking distance though thanks to a double digit lead among independents in both of those contests.
If Lisa Madigan made a surprise decision to run for this seat it would be no contest, as she leads Kirk 49-33.
Full results here.