If I wanted to vote for a Liberal, I would do as most American voters have in the past: vote for the more Liberal in the Liberal party. McCain alone, or with the Liberal past of Romney tacked on, is only going to erode his support among the Right. The squishy Center will decide at the end as usual that they want the real deal.
That's not the point. The point is, is that there is a dearth of qualified Republicans for VP who has Gubernatorial experience. If you want McCain, who is already a flawed nominee to begin with, to pick Crist, Perry, or Huckabee, go for it, and you'll see even more conservatives staying home in disgust. If you want him to pick untested & unqualified potential nominees such as Palin, Jindal, Pawlenty, Sanford, or Rounds, go for it, which will neutralize Obama's dis-qualifications and he'll end up winning.
From a logical standpoint, Romney is the no-brainer choice for VP. He's got the money, the experience, and the executive skills who can be president in a pinch. He is libertarian on economic issues, supports the WOT, and he has always been center-right on social issues which will improve if he's the nominee. Complaining about Romney isn't going to get anyone anywhere - it's bad enough we have McCain. Time to make lemonade out of lemons and work with the choices arguably not given to us.