The campaign hasn't even really started here yet. Once the commercials start and the volunteers mobilize, Quinn will get a boost. A lot of those Rauner voters are Democrats who don't like Quinn but will switch their vote when they find out about who Rauner is.
I doubt it. If Brady only lost by 1 (and he's the worst candidate for Illinois) and Quinn has gotten more unpopular since, then I think Rauner has a good shot.
It was also the best year for the GOP since 1994 and the GOP picked up the Senate seat that year, so I would by no means count Quinn out. The Cook County machine may not be enough to eke it out this time, though.
I'm not counting Quinn out - not only is Illinois democratic to extreme levels, but Quinn seems to be quite politically adept or at least very lucky, and Rauner is not the best candidate they could've run (he's basically a pro-choice Scott Walker). At the same time, Brady was basically a generic "Tea Party" conservative, who, even in a Republican year, was too incompetent to seal the deal, so Rauner is a significant improvement of sorts.