Of course, to determine whether collusion occurred, we would have to know whether the Trump campaign continued to meet with Russian representatives subsequent to the June meeting. The early “courting” stage is almost always somewhat open and discoverable. Only after the Russian intelligence officer develops a level of control can the relationship be moved out of the public eye. John Brennan, the former director of the C.I.A., recently testified, “Frequently, people who go along a treasonous path do not know they are on a treasonous path until it is too late.”

Even intelligence professionals who respect one another and who understand the Russians can and often do disagree. On the Trump collusion question, the difference of opinion comes down to this: Would the Russians use someone like Mr. Goldstone to approach the Trump campaign? Our friend and former colleague Daniel Hoffman argued in this paper that this is unlikely — that the Russians would have relied on trained agents. We respectfully disagree. We believe that the Russians might well have used Mr. Goldstone. We also believe the Russians would have seen very little downside to trying to recruit someone on the Trump team — a big fish. If the fish bit and they were able to reel it in, the email from Mr. Goldstone could remain hidden and, since it was from an acquaintance, would be deniable if found. (Exactly what the Trump team is doing now.)