I'm not seeing a whole lot of polling data on this race yet, but according to the Wilson Research Strategies group, Obama maintains a nice lead
Obama has 16 point lead in Illinois Senate Contest
Obama [leads] Republican Jack Ryan by a healthy margin 44% to 28%, with other candidates combining for less than 5% and 18% still undecided. […]
"Clearly, if Ryan has any hope of making this a competitive race he must do two things, first continue to grow his lead with Republicans and find a way to communicate with Independents," Adams said. "With 33% of those surveyed self describing as independents, the Independent vote will play a crucial part of any winning coalition and right now Obama is doing a better job of winning their trust."
Undecideds are a higher percentage than the margin Obama holds, but they'd all have to break to Ryan. That doesn't seem too likely considering:
Obama has a commanding lead among Independent voters leading 44% to 15% among those self described as being registered Independent. Obama also leads Ryan among men 41% to 31% and women 46% to 24%.
The race will certainly tighten, and Obama's campaign will try to downplay the significance of polls like these, but from where things stand, it's difficult to imagine a scenario where Ryan pulls this one out.