The news out of last week’s Cheryl Mills deposition was that the Clinton confidante didn’t say much about Hillary’s email server. Which only goes to show that Mrs. Clinton has a serious problem—and she knows it.

This is, after all, Cheryl Mills. For more than 20 years, she has served as the Clintons’ very own Winston Wolf (Harvey Keitel in “Pulp Fiction”)—their fixer, their problem-solver. From impeachment right up through Benghazi and the server, Ms. Mills is the one constant in the behind-the-scenes obstruction. The less...