You are, of course, assuming that he wasn't lying to you. After all, he made a commitment to his local paper that he wouldn't support "extreme" nominees.
So, take your pick. Who was he lying to? The GOP, whom he disagrees with, or the newspaper, whom he agrees with?
He can either betray the party and lose his seat or vote with us and face the possibility of losing his seat. Whatever happens, let's look on the bright side: the 2010 primary!