On the morning of November 28, Ukrainian law enforcement did something it had never before done in its history: It showed up at the apartment of the head of the president’s office to investigate him for graft. Commentators around the world have noted the strain that an unfolding scandal has put on the Ukrainian presidency at a time when the United States is pressuring the country to make concessions to Russia. But just as striking is the fact that an investigation into energy-sector kickbacks