Why has U.S. national security policy scarcely changed from the Bush to the Obama administration? And why does it matter? The theory of 'double government' posed by the 19th century English scholar Walter Bagehot suggests a disquieting answer. The public is encouraged to believe that the presidency, Congress, and the courts make security policy. That belief sustains these institutions' legitimacy. Yet their authority is largely illusory. National security policy is made, instead, by a 'Trumanite network' of several hundred members that is largely concealed from public view.