Other unreliable GOP senators: Stevens (AK), Murkowski (AK), Hagel (NE), Lugar (IN), possibly Isakson (GA), sometimes Hutchison (TX), occasionally Domenici (NM), the humiliated (by the British MP) Norman Coleman (MN). It's a list much too long. Even Burns (MT) though he votes conservative is worried about a challenge from the Democrats in 2006. I would not be surprised if he moves to the left.
I dislike predicting it, but I would hazard a guess Mel Martinez from Florida will join those ranks on some issues.