With the resignation of Dana Boente on Friday as U.S. attorney for the Eastern District of Virginia, President Donald Trump has an opportunity to replace another Obama-era holdover in the Department of Justice line of succession. If Trump demands that the department fire Special Counsel Robert Mueller, and if enough officials resign or get fired rather than carry out his order, the decision to do so could fall to Boente’s successor. As Attorney General Jeff Sessions has told the Senate Judiciary Committee, Trump has been interviewing candidates for some of the 93 open U.S. attorney positions. Democratic lawmakers and legal...