I like Clark. I like Sebelius, although I could see the problems that it would pose in terms of the perception that it "replaces" Hillary, even though I don't necessarily agree. Clark would be my pick overall, but his experience quotient is similar to Webb's. I don't like Webb and Richardson would be problematic for Hillary supporters ( I would have a hard time with it, I'd still support the ticket obviously, but still). Honestly, either Clark or Sebelius or Hillary (even though I don't think Hill would take it)

Sorry about the stream of consciousness, I'm a bit tipsy.