Christianity, as an historical phenomenon, can be seen as a form of slave morality, as it shares with it resentiment
toward life itself, towards Others, and most especially, according to Nietzsche, towards one-self.
While N. was more concerned with the "politics of the soul" his stance towards nations and the state, which he called the "coldest of cold monsters," was one of disdain. One can argue that N. understood politics as another herd perspective.
I think, when you ask if leaders are "masters," that you have missed the essence of "master morality," and N. would have considered them as much (if not more so) a representative of slave morality as the herd that follows them.