Does anybody remember the NBC show Kings from back in 2009?
It was basically this exact premise, a supernatural modern political drama. Ian McShane played the king, and was amazing as always.
It got cancelled after one season, because it was several years too early for the “Prestige Television” era, and because the network didn’t really know what to do with it. It was really good though, I think you can still stream it via Hulu.