I honestly think his election was a fluke. Illinois will have enough sense to fire Scott Walker Rauner 3 years from now.
Illinois has a long history of electing Republicans as Governors, and had a longer streak than Massachusetts from 1977-2003. In the past 50 years, the only times the Democrats have won a majority of the vote were 1972 and 2002. 2006 Blago was unpopular and already scandal-ridden, but the Democratic wave that year probably saved him. In 2010, Republicans nominated a garbage candidate when they should've won easily.
If Hillary is President, I can see him skirting by in an inverse-2010 in 2018 if it's another low turnout Republican midterm wave, and he maintains his numbers in the suburbs (though even then, I wouldn't bet on it, personally).
Illinois isn't completely gone for Republicans at the state level, despite all the hate he gets from the red avatars on this forum.
Except, 2018, is the inverse of what 2010, was in governor elections, where there are term limited govs, that are Republican, instead of Democrats.
Quinn almost won, with Paul Vallas. Clearly, Lisa Madigan will be favored if she is nominated.
