“Even setting that aside, the Mueller report sets out substantial evidence that Trump criminally obstructed justice in at least some instances. The former Justice Department and FBI official Chuck Rosenberg has said that, in the absence of the Justice Department guidelines against the indictment of a sitting president, as a prosecutor, he would have brought an obstruction case against Trump. Former U.S. Attorney Preet Bharara and former Deputy Attorney General Sally Yates have made similar arguments. And while lawbreaking is not required for impeachment, it is notable both that all three serious efforts to impeach a president in U.S. history have involved allegations of legal violations and that two of those three instances—against Richard Nixon and Bill Clinton—concerned criminal behavior, specifically obstruction of justice.”

Source: Reasons for Impeachment, Beyond the Mueller Report – The Atlantic