In a special report, MSNBC Chief Legal Correspondent, Ari Melber, walks through the historic Mueller probe and breaks down why is has been the most effective probe into an administration since Watergate. Melber examines how Mueller demonstrated “government professionalism” and “prosecutorial rigor” that was “a rebuke to Trump’s entire political existence.” Melber concludes that through his actions, Mueller showed the tougher path to “following evidence, not assumptions.”