Attorney General Merrick B. Garland is the public face of the government’s unprecedented effort to identify, arrest, and prosecute those connected to the Jan. 6, 2021 protest at the Capitol. But the person handling the day-to-day management of the one of the largest and most politically freighted efforts in the history of American law enforcement has largely flown under the radar: Matthew Graves, the U.S. attorney for the District of Columbia.