I'm of the believe that they are all the leaker, and that this whole thing was started because they all wanted to make the knowledge public while still having plausible deniability.
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After all, have any of the leaks really had anything incriminating? There is no "lets find out a way to screw this person" type of conspiracy as found in the Easter European emails. Most of them are debates between different people and show very little "collusion" or anything that wasn't taking place in public.
Of course, a few people are seen as two-faced, or shown to hide how they really feel. But that isn't anything new or ground breaking.