Reply #16: I think it has something to do with the fact that no matter how liberal

[AP]

Clark is, most Democrats accurately perceive the military as a very conservative institution.

Clark appeals to a very small segment of Democrats who find the military an institution much more compelling than your average Dem finds it, and his appeal to that group is immense since he's as good an example of a 'liberal' military person as you'll find (many starred general, top of his class, voted for a few Republicans in the past and hates genocide, but still making money on Wall St in retirement).