Brownback and Deal are very unpopular. We may be seeing the consequences of low approval ratings. It is possible to have a low approval rating as an incumbent and still win... but it is about a 50% chance of winning for someone with an approval rating of 44%.
So how can Democrats exploit weaknesses of right-wing incumbent Republicans in R-friendly states? Bread-and-butter issues.
We can exploit Walker's weakness as well in a Democratic friendly state concerning corruption.
I agree on that. Also Corbett in Pennsylvania for corruption, LePage in Maine for being out of touch with reality, and Snyder in Michigan for betraying workers to out-of-state interests (states clearly D), and Scott for cronyism (Florida is about 50-50 D/R).