For the first time in American history, a former president faces at least one criminal trial. Prosecutors in other countries have convicted their leaders—in France, Israel, South Korea and Italy, to name a few—but the idea of American exceptionalism makes us think that our presidents won't be hauled off to prison. Of course, President Richard Nixon escaped indictment by a pardon, and his vice president, Spiro Agnew, resigned with a plea of "no contest" to avoid a criminal trial; and there have been quite a few governors, senators, mayors and other elected officials who have been indicted or wound up behind bars. Because the rule of law is central to our democracy and thus nobody is above the law, including former presidents, we are now witnessing a once-and-perhaps-future leader of the free world in the dock.