Democrats and the media are accusing anyone who criticizes special counsel Robert Mueller as Trumpian conspirators trying to undermine his probe. But who needs critics when Mr. Mueller’s team is doing so much to undermine its own credibility?

Wednesday’s revelations—they’re coming almost daily—include the Justice Department’s release of 2016 text messages to and from Peter Strzok, the FBI counterintelligence agent whom Mr. Mueller demoted this summer. The texts, which he exchanged with senior FBI lawyer Lisa Page, contain...