Could it mean our self, our thoughts and actions; some kind of deep, personal counter agency, an anti-, alter and adverse ego?
In the spiritual, is the enemy the flesh as Paul described, “the war within”; the cause of internal conflict, struggle?
Beyond our self, is “the enemy within” someone or -body among our closest ties that works intentionally or not to undermine us, even defame us as something or someone we're not? Can a so-called friend or family tie be our worst enemy?
A film by the same name is about a plot at the highest ranks, the presidency; a military coup. Certainly, coups happen but here, in the United States? It can't happen here, can it?
In The Dictator’s Handbook, Why Bad Behavior is almost always Good Politics, Bruce Bueno de Mesquita and Alastair Smith assert:
Leaders do whatever keeps them in power.
If the case, how far will they go? Is our “best interest” they’re interest or is our welfare worth anything?