In a letter disclosed Monday in a federal court filing, the FBI confirms one of the world's worst-kept secrets: It is looking into Hillary Clinton's use of a private email server.

Why say this at all, since it was widely known to be true? Because in August in response to a judge's direction, the State Department asked the FBI for information about what it was up to. Sorry, the FBI said at the time, we can neither confirm nor deny the existence of any investigation.