Rauner will win, atlas is never right.
In all seriousness, he is underestimated as a candidate and out of staters don't understand the pathological hatred of Michael Madigan by the majority of Illinois and the Republican war chest that will remind them. Tossup.
I'd be willing to bet most people in Illinois don't know who Michael Madigan is, tbh. Atlas mistake #1 is to all voters have as deep a knowledge into their state's inner workings as you do.
There was some poll posted here a while back that asked IL residents who they blamed most for the state's problems - Madigan or Rauner - and Downstate, Collar Counties, and Suburban Cook County all said Madigan by big margins. The city of Chicago blamed Rauner, but I believe the margin was a rather underwhelming 52-35.
To add to Dwarven Dragon, this last cycle the entire Pub message for legislative seats was about Speaker Madigan. Pubs won a net of 2 Senate seats and 4 House seats on that message. Dems were close to losing a few additional seats in the Chicago 'burbs even though Clinton was racking up big margins. Even some House Dems are
now questioning the direction under the Speaker.
Poll
