Scott Walker is the one fly in your ointment. Starting in 2010 the DemoCraps threw every bit of political and legal dirt at him that they could find through two successive campaigns and a "John Doe" investigation. Nothing stuck. That alone makes him the strongest possible Republican candidate for 2016.
I hold out great hopes for Scott Walker. If her comes up with another ethanol-like statement, however, he’ll be well on his way to tearing himself down.