Why won't the Libya story go away? Why can't the memory of U.S. Ambassador Chris Stevens and his staff be consigned to the same sad-and-sealed file of Americans killed abroad in dangerous line of duty? How has an episode that seemed at first to have been mishandled by the Romney camp become an emblem of a feckless and deluded foreign policy?

The story-switching and stonewalling haven't helped. But let's start a little earlier.

The...