I think Neil Sinhababu is right to think that the media’s disproportionate interest in obviously doomed presidential candidates like Jon Huntsman 2012 or Joe Lieberman 2004 has to do with the general fact “that major media outlets tend to take great interest in people who loudly criticize their own parties from the center.”
In general, it’s important to appreciate that intra-party conflict plays a very special role in the American media. Operating in a kind of truth-free zone where there’s no objective reality, the closest thing to a “fact” is when all members of one party and some members of the other party agree on something. Consequently, there’s never a greater media darling than a member of congress from a contested district who’s willing to take time out of his busy day of legislating and winning re-election to go whine about the party leadership to a reporter from Roll Call or Politico. When someone does it in the course of a national political campaign, it’s an even bigger deal!
None of this would be necessary if journalists felt more comfortable running headlines like “Rick Perry Denies Truth Of All Of Modern Biology” absent an added frisson of horse race conflict. Then you could strictly separate the issue of is Perry talking nonsense about biology (yes!) from the issue of which people could plausibly win a presidential election next year.