I just watched an interesting clip that illustrates how Clark faced the Shelton smear when Milosevic resurrected it at The Hague:
http://www.videos4clark.com/vidclips/TW_12_21_03.WMV
Watch this George Stephanopolous interview for a key moment in Clark's trial at The Hague against Slobodan Milosevic. Clark responds very calmly and effectively, and under some significant pressure, considering the circumstances. I'm sure he knew it was coming--he knows Milosevic inside and out.
Of course, the fact that Clark's received the Congressional Medal of Honor and has been knighted by the British and the Danes kinda helps with his "character and integrity," too. And then there are all those endorsements from those who have worked with him... :)
Facts to consider:
Gen. Shelton is an advisor for John Edwards.
Clark wanted the option of US troop deployment on the table for Operation: Allied Force, and went around the Pentagon to argue his case.
Gen. Shelton strongly objected to not only using US ground troops to support NATO in stopping Slobodan Milosevic's ethnic cleansing in the Balkans, but in Clark's aggressiveness in advocating the option. Shelton convinced Clinton to rule it out, and Clinton announced the US wouldn't consider a ground invasion.
Clinton later admitted this "casualty averse" approach was a mistake.
Gen. Shelton said Clark has "character and integrity" issues the first week Clark entered the race, but has refused to elaborate. Clark said, that with no specifics to defend against, it's the equivalent of McCarthysism--attacking someone's character without any proof.
The smear has been "hearsaid" by Generals Tommy Franks and Norman Schwartzkopf, neither of whom have worked with General Clark.