A president defying Congress. Disrespect for the law. Attacks on the press. Evasion in the courts. The privatization of war. Quid pro quos with foreign nations. The mounting dangers to American democracy have long been with us. But all these perils first emerged together during the Iran-Contra scandal of the Reagan-Bush era. This opaque foreign policy mess has receded from history, a minor speedbump at the triumphant end of the Cold War. With American...