Santorum lost his home state by 18 points last time around. There is a heavy stink associated with any incumbent who loses in that kind of landslide defeat. I actually agree with Santorum on most issues and he is a solid conservative in my book, but he will never attract the kind of money needed to truly make him competitive. Few people are going to risk big money on a guy who lost his last re-election bid in such spectacular fashion. And yeah, I think you have a good point - Santorum is very plain and not flashy (I'd call it charismatic) enough for the media.
Stink doesn't come with losing. A bit might come from running for higher, much higher, office on the heel of such a loss. I like Santorum, I hope he succeeds in gaining elective office, and that I'll see him again on the nation stage. He's not a winner this time around.