Pete Abel makes a good deal of sense to me:
1. McCain raises the ire of the contemporary Republican establishment because he rejects their meaner instincts. As I've written before, McCain decries torture while the Establishment excuses it. He fights pork-barrel spending while they enable it. He calls for policies to combat global warming while they deny it. He seeks reasonable compromises on immigration policy while they stoke fear and prejudice.
2. McCain represents for Republicans what Obama represents for Democrats: a meaningful step away from the last 15-plus years. I'm not saying either man will revolutionize partisan politics as we know it, but both promise (at a minimum) evolutionary progress toward a different America. And if we truly believe country is more important than party, then we owe it to ourselves to boost the two candidates who (among all their peers) represent the best hope for moving us in a post-partisan direction, regardless of our individual party loyalties.