Although his questioners at the time didn’t know what he was talking about, Fusion GPS chief Glenn Simpson raised eyebrows on Aug. 22, 2017, when he told Senate Judiciary Committee investigators that the FBI had a “human source” inside the Trump campaign.

It’s still not clear what Simpson meant. Was he referring to Stefan Halper, now recognized as an FBI informant who tried to insinuate himself into the campaign? Or was it someone else? Congressional investigators still don’t know. But in light of the attention paid to Halper, it’s still worth going over precisely what Simpson said last year.