I know exactly how they differ. To wit:
Winning the primaries requires only that you appeal heavily to your base (in Pres. GWB's case, the right-wingers), making promises that "push their buttons."
Winning the general election requires turning on the dime and ignoring your base, while appealing to those who voted against you in the primaries (the liberal RINOs who voted for McCain), and appealing to those who otherwise agree with your new, more liberal opponent.
Isn't that how Pres. Bush won?