We really have no assurance that McCain won’t foist another Souter onto us if he gets the chance. Why would I or any other conservative have any reason to trust him?
We needn't trust him. He's the nominee. All we have to do is measure the odds. What are the odds of getting a Souter with McCain vs. the odds of getting a Souter with Obama or Hillary. For me, that's pretty simple math. Doesn't guarantee anything, but picking the better option is really not that tough. Trust has nothing to do with it.
McCain is what he is. An obnoxious jerk.
Would you trust Hillary or Obama to give you a conservative?