Ever since a “senior official in the Trump administration” penned an anonymous 2018 New York Times column attacking President Trump as unfit for office, Washington has been engrossed in a high-stakes whodunit. After an exhaustive investigation, the White House believes it’s cracked the case, identifying Trump's turncoat as his former deputy national security adviser, Victoria Coates, according to people familiar with the internal probe. Rather than fire Coates, the White House has quietly transferred her to the Department of Energy, where she awaits special assignment in Saudi Arabia -- far from the president. Trump effectively demoted Coates just four months...