Cubreporter is right imo, because Clark doesn't like to be challenged, he's a GENERAL dammit! The man is an egomaniac and he's ready to blow any time now. Additionally Clark has a bad habit of spreading lies and innuendo to prop himself up. Whether to make himself look like he's on the inside or important or the uber prop up; the presidency.
Personally, I have my fingers crossed for a Dean/Clark ticket. :-)