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Louis Foxwell is correct.
Without a conviction it would be impossible to establish which treason was being pardoned. (Known treason, or undisclosed treason?)
Your view of the constitution is way too simplistic.
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Obama wouldn’t even mention treason or specific offences, and wouldn’t need to. He would likely do a blanket pardon as Ford did for Nixon, covering all possible “offences” and covering the dates of Shrillary’s tenure as Secretary of State. I’m not saying he definitely will do it, I have no idea how he views the matter, but precedent exists, of a kind, if Obama wants to do it.