I’d look for whoever in the administration most vociferously denounces the author of the op-ed. My advice is based on my own experience. I have to be a little vague about this. In the late ‘90s, I was given by a second or third hand source a document showing that the Clinton administration had seriously misled the public.
I didn’t know the ultimate source, but I was able to verify that the document was authentic and published the article, which created a minor furor in small circles.. A week later, the New Republic got a letter from a DC lobbyist denouncing the article and denying its claims. Several years later, I heard that the ultimate source of the document was that lobbyist. That’s how Washington works. So listen for the loudest repudiation of the op-ed author.