Democrat Senator Burton Wheeler was the person who actually leaked it to the Chesley Manly, Washington correspondent who then published his story in the Tribune and the Washington Times-Herald. As to where he got it from its hard to say. Major Wedemeyer (his name may ring a bell) is a possible suspect since he was in the planning office and actually authored a lot of the plan. He also was the son-in-law of General Embick and both had open connections with the America First crowd. Other suspects include FDR himself (unlikely), Hap Arnold, and even British agent William Stephenson (Intrepid).
Quite frankly I think is was someone who had access to it (there were a couple hundred who had access to the 36 copies), and had some affiliation with the America First group. I can’t narrow it down from there but neither did the FBI so I guess that’s OK. 3 days after the leak they became “distracted” by other world events.
One of the topics on my short list is Merrill’s Marauders, since that’s where my grandfather (on my Dad’s side) served so I see where you get your interest in the topic.
Maybe a more practical suggestion for a paper would be an anlysis of the U.S. strategy in the Pacific. Was it really necessary for Homer’s dad to retake Leyte for Gen. MacArthur or was it just PR? How about all those nasty islands. The whole theatre seems murkier to me than the ETO. Maybe that’s just me.