The basic point is, we and the Russians were talking "at the highest levels" as they say, and Trump was trying to convince the Russians that we have a mutual interest in finding and stopping ISIS. They've already had one commercial flight downed by a terrorist bomb onboard, as have we, and we've been talking about bombs concealed in laptops for weeks. (
For years, really, except it wasn't laptops in 1988.)
So to convince the Russians, Trump says "Look, we've got really good intelligence with a really good source that tells us this is a real plot. You really want to get on board with this, because ISIS hates you as much as it hates us."
This information -- "we've got really good intelligence with a really good source" -- is probably code-word information. Even more so if he said "really good source within ISIS" or "on the ground in Iraq." But it's still a legitimate tactic: I think the term of art in diplomacy is "putting one's cards on the table" or "opening the kimono." You're offering something to prove you're sincere and to show the risk is real.
So let's assume that this is what really happened. What we know the mysterious anonymous source said is that Trump "revealed code-word information." And we know that General McMaster, who has pretty much always been the definition of a straight shooter, said that the release was "wholly appropriate." He also said that Trump didn't know the source, so he couldn't have revealed it. Like the "Cardinal's" real name, that's entirely plausible: he wouldn't have the need to know.
Here's the trick: all these statements can be true! Trump did reveal code-word information, and it was wholly appropriate.
The moral of this story is pretty simple: it's entirely possible that Trump did what the anonymous source said, McMaster was telling the truth, and -- pace
Jim Geraghty -- that there is a perfectly valid reason why Trump wanted to do it. But if you
start with the assumption that Trump is a cad, a fool, and a blackguard, you're unlikely to see that. And any news story you write is unlikely to consider that.