There actually could have been a viable path for him to the nomination. The way I see it, he should have resigned as ambassador, then penned a tell-all book about all the abuses in the Obama administration. Go after Vann Jones, all that crap. "The President asked me to serve my country in China, and I did. But I could not in good conscience continue serving in the worst administration in American history." Talk about how Obama is the worst jobs President since Herbert Hoover. After Obama releases his birth certificate, demand to see his academic records. Basically, the Donald Trump route, but with executive and foreign policy experience.
Would it work? Probably not. And he probably wouldn't want to do it. But hey, if he had hired me as a consultant instead of that wuss John Weaver, he might actually be at 5% in national polls.