Within 24 hours of the 9/11/2012 consulate attack, US intelligence knew that Al Qaeda was likely responsible. (This should not surprise us, since that information leaked almost immediately.) But for some reason (despite the concerns of wiser officials), the Obama administration for days peddled nonsense about how the attack was a spontaneous response to a YouTube video.
UPDATE: Eli Lake has a partial explanation of how this might have come to pass. It seems that the CIA issued a “talking points” document that suggested that the attack was spontaneous, and the administration was using that. Still unanswered: how it happened that the CIA put out a document that was at odds with everything they knew, and why the White House and State Department were so unskeptical about a story that contradicted everything that was being reported.