Clinton will head the top of the ticket, but only after a brokered Convention. She sure isn't going to get into the fray and have to answer any straightforward questions on any camaign trail.
Edwards is the perfect match. He is a boyish-looking, Camelot-appearing lightweight who won't give her any trouble in the #2 spot, will "represent" the South, and bring in scads of money from the trial lawyers.
As for Mousely Clark, he is a stalking horse to keep some amount of support "uncommitted" *wink, wink* and be first in line for SecDef as his reward. He and Edwards will throw their support to the Hildabeast at a critical moment in the power-brokering process.