Revenge, anyone? John McCain is being wooed by publishers to write a book on Sarah Palin, who's been dissing her former running mate as she promotes her own new tome. Sources say McCain has gotten a few big-bucks offers — and they expect he'll bite. "John [isn't] going to sit by and let her version of the truth become fact," an insider says of the two (l.). "He's a fighter who wants to protect his campaign's legacy — plus being offered $8 million doesn't hurt."