Just a setting thing that I thought of:
Only kings and their immediate children can be clerics, because they are divinely blessed by blood. There are still lots of priests running around, but they are not spellcasters, unless they are a mage. While I think the King and the country would worship a god (or even more than one god), the king may also act as a living saint or even the god of his country.
Because the King has divine spells, he can just say, "It's obvious why I am King, as no one else can do the things I do. God wants me to be King." And it's quite likely a sizable portion of the uneducated populace would believe this without reservation. Shrines to the King might even be kept in villages for everyone to pray at. And the normal taxes would be considered a tithe to him freely given, instead of forced taxation.