Personally, I am not much alarmed that several of Mueller’s staffers have anti-Trump political views. But as more evidence emerges, I have become increasingly disturbed about whether those views will taint perception of the Mueller investigation, particularly in the case of Andrew Weissmann, a key Mueller deputy. A gifted career Justice Department lawyer, Weissmann sent former acting attorney general Sally Yates an effusive email shortly after Yates was fired for insubordinately defying Trump on enforcement of the so-called travel ban. The obstruction aspect of Mueller’s investigation calls for an objective evaluation of how much independence law-enforcement officials have from the chief executive. Weissmann’s lauding of Yates suggests he is not objective on this point.

For Trump, the best outcome is that he leaves Mueller in place and is exonerated. For Mueller, the best outcome is that the public accepts the integrity of whatever decisions he makes. In that regard, I began with the belief that Mueller was a superb choice whose well-earned reputation for personal integrity would be critical. I still think so, but I’ve been shaken by his puzzling insensitivity to the imperative that his staff be, and be seen as, driven by evidence, not anti-Trump bias.