I think Mike Castle is right on this one. He lost a very bitter primary where Christine O'Donnell made such vicious personal attacks on Castle and his family that he can't support her. I get that. He also won't support the Democrat. He shouldn't. He's a Republican. He should support other Republicans, even if he isn't supporting O'Donnell. Endorsing Glenn Urquhart for his current job would be a start.
What you don't do is what Lisa Murkowski is doing. She lost. She should accept the voters' decision and move on. By running, she's saying she's more important than the party and that she's the only one who can represent Alaska. It's about her, not about Alaska. Arlen Specter thought he was more important than anyone else and irreplaceable. Charlie Crist feels the same way. When you run you accept that you are running on a party's ticket and you have certain responsibilities to the party. This is a two way street.