That funny, I thought all black men were supposed to be called 'Reverend' as soon as they get involved in politics. Aren't they all self-ordained Reverends? (when I see a black man on the news, I automatically assume that he is a Reverend...maybe I'm wrong, some of them are ministers.)
Reverend is the title, and Rev. is the religious equivalent of Mr. Sometimes it’s used colloquially when people speak about “the Reverend” without using the last name.
Priest is generally restricted to Catholics, Anglicans, or occasionally Lutherans, I think. But most Protestants would use Minister or Pastor or Preacher or the like.
A fair number of black politicians either used to be ministers of a church of some kind, or else just use it (I suspect) as a device to cut their income taxes.