In those fraught days after the firing of James Comey, why did Deputy Attorney General Rod Rosenstein appoint Robert Mueller, in part, to investigate the cashiering of Comey that he was party to, and without specifying the crime that the president was being investigated for, as required under the special counsel regulation?

The appointment of Mueller was so key because once you have a special counsel, even one who is highly professional and judicious, you have an investigative beast roaming the landscape that will inevitably command an enormous amount of press attention and, past experience shows, find crimes to prosecute even if they are removed from his original charge.

Of course, this is precisely one of the reasons why Mueller had such fervent support among Trump’s detractors. But there is no reason that Barr should share their assumptions, or their horror at the idea of finding out more about the investigation that, for two solid years, they portrayed as the single most important event in American public life.