It's fair to say that John McCain's failure to attend CPAC this year was a huge strategic mistake. Woody Allen once said, "Eighty percent of life is just showing up." He was right. John McCain was wrong.
Because I cannot believe McCain's top-notch advisors would advise him to skip CPAC, I tend to think the candidate is running the show. Just as only a fool would represent himself in court, only a fool would run his own campaign.
By dipping his toes in the conservative movement, speaking at some events (such as Liberty University), but avoiding others (such as CPAC), McCain has made the worst of both worlds. He has lost some of his appeal as a maverick -- but he has failed miserably to gain the support of conservatives.
In any event, it appears the campaign that once wanted to stress inevitability has failed to wrap things up early. I have also heard rumors of a staff-shakeup -- as well as rumors that John McCain's staff was actually unaware he would be "announcing" on Letterman. This is just a rumor, but it's at least plausible (given his recent mistakes).
Missing CPAC is symbolic of the reason conservatives do not trust him. If Rudy Giuliani can show up at CPAC, how can McCain justify being the only candidate not to make an appearance?