Plenty of loyal republicans are voting based on who they think can win, not on how much they'd like.
The republican party is not a church with an inflexible code and priests hurling anathemas at any who deviate from it. It is a practical institution that elects half of the successful pols in the country. Many of those pols are far to my left, and no doubt yours. I don't control them, I don't own the party, I couldn't read them out of it if I wanted to. And neither can you.
McCain can’t win because the conservative Republicans will not support him.
McCain has been making all sorts of promises to win over conservatives, that he really can’t keep. He promises to make the Bush tax cuts permanent, but the president really has no power to do this. He promises to build the border fence, but he probably couldn’t get that done, either. He promises to keep fighting in Iraq, but he also mentioned benchmarks, the very same thing that he accused Romney of.
McCain’s promises are much like Huckabee’s fair tax promise,
all talk, no action, because in the end, it’s up to the congress.