My hunch is that Clark is a prima donna, a ring-knocker, and a glory hound. Both Shelton and Franks are famous for their muddy boots (Shelton: ROTC, Special Forces; Franks: College dropout, junior artillery officer in Vietnam) and their loyalty to, and undisguised affection for, their men. This is in stark contrast to the West Point grad and Rhodes scholar Clark, who moves among politicians, journalists, diplomats, and (more recently) A-list Democrats. Note his comments on John Kerry, saying that Kerry was "just a lieutenant" whereas Clark was a general, which, he implied, gave him some kind of foreign policy credibility experience. This is, on its face, a ridiculous claim, even if you ignore the fact that Clark had exactly enough credibility to be dismissed from his post. Besides, say what you want about Kerry for god's sake, but the guy's been in the senate for almost 20 years. I think he knows a bit more about international relations than your basic lieutenant.
So Clark is still a cipher in this race. Nobody seems to know the whole story; more precisely, those who know aren't saying. Clark won't win New Hampshire, and he probably won't even beat Dean there, settling for third. Perhaps that's not fatal, but the test will come in the south. I don't think Clark's message will sell in the south, which is why he's swinging hard in New Hampshire and hoping for a boost. Without some great press and a bump in the polls, his sell-by date is coming up, maybe on February 10th, when the Virginia and Tennessee primaries roll around, or March 9th, when Louisiana, Florida, and Mississippi poll. If he can't win going away in those states running against a bunch of Yankee liberals, he's toast.