It's posted on TPM on the "Editor's Blog" and the byline says "Josh Marshall is editor and publisher of TalkingPointsMemo.com." what else do you need on his credentials?

There are links scattered throughout, but part of the point of this post is that no one is really talking about this issue at least at the depth it deserves, so understandably it's light on references. In this case, I'd treat a lot of this as an original source.