However, if his vote wasn't needed, why not vote his principles, or
if you vote was needed why not vote against and send the bill back to committee and rally like minded people around his position.
Santorum's bottom line is that his "principles" are and always have been negotiable.
That said, if Santo happens to be the nominee I will vote for him. But I will do so with a more complete understanding of what we would be getting than some of his most ardent supporters.
A recent Rasmussen poll shows that only 17% of the voters think that Santorum can beat Obama, while 58% think Romney can. This is not among Republicans either, this is among all Americans, independents included.