The instant Palin exposes her "principles" by backing McCain over Hayworth, the lemmings will start racing for the cliff.
There are just a few problems with your premise:
1. An endorsement may not be forthcoming. You're just speculating.
2. Loyalty is a principle, too.
3. If Palin believes that McCain can keep the seat for the GOP and Hayworth might lose it to a Dem, her endorsement would be completely consistent with conservative principles.
4. If Palin was without solid onservative principles, she wouldn't have even run against Murkowski, much less beat him like a drum.