Cheney's office denies ever giving him this mission. This was purely a CIA op. That's what got Scooter going. WHY WOULD JOEY CLAIM CHENEY SENT HIM WHEN HE KNEW IT WAS NOT TRUE?
Wilson didn't claim that Cheney sent him. He claimed that Cheney knew he debunked the Niger forgeries after he made the trip (which is a lie, of course). He said that Cheney HAD to know that he'd debunked the forgeries because Cheney's the one who asked the question of the CIA and, of course, would have been given an answer. He said that Cheney was lying about not knowing about his supposed debunking of the Niger papers.
This claim, not who sent him, is what is important--it goes to the heart of the political battle going on right now--was the public mislead before going to war.