Until today, I have defended Mueller against the accusations that he is a partisan. I did not believe that he personally favored either the Democrats or the Republicans, or had a point of view on whether President Trump should be impeached. But I have now changed my mind. By putting his thumb, indeed his elbow, on the scale of justice in favor of impeachment based on obstruction of justice, Mueller has revealed his partisan bias. He also has distorted the critical role of a prosecutor in our justice system.