But why would a man of integrity, at a time when the nation is already inflamed, add gasoline by insinuating wrongdoing by the presidential front-runner even though he admits he can’t “yet assess whether or not this material may be significant”? And give Clinton no chance of exonerating herself by saying “I cannot predict” how long it will take to assess the material?

The most benign, and likely, explanation is CYA: Comey wanted to inoculate himself against future allegations from Republican lawmakers that he sat on relevant information before the election. If so, self-preservation trumped his professed love of transparency. 

By falling short of his own standards of transparency, Comey is harming both election integrity and his well-deserved personal integrity. He needs to explain himself if he hopes to salvage either. —Dana Milbank