When ISIS last year called for the destruction of the Yazidi people, President Obama said that would constitute genocide and he ordered U.S. forces to keep it from happening. Human rights advocates say Christians now face a similar threat Nina Shea directs the Center for Religious Freedom at the Hudson Institute.

Many who later lost faith in Fidel Castro can remember how they once admired the man who needed just a dozen men to launch the Cuban revolution.

The collapse of the Soviet bloc ended the massive subsidies that had kept the Cuban economy afloat. The once-vaunted education and health care systems fell into disrepair. Fidel Castro's stubbornness, meanwhile, made political and economic change difficult in Cuba.

Trump has always talked about how important in dealing with foreign leaders, how important it is to establish a good personal relationship very close to what Pope Francis says, so they may both really want to emphasize their development of a personal relationship.

Hispanics are the fastest-growing evangelical group in the country right now, an important constituency. But Trump's views, especially his views on immigration, did not exactly go over well with this faith constituency. Rev. Rodriguez told me that Trump's invitation created something of a stir in his world.

The letter writers span the spectrum from left to right. Members say they don't want this to become a partisan political issue. In fact, there are reasons administration officials have been cautious in making a genocide declaration.

ISIS goes after any group that deviates from its extreme ideology, dissident Muslims, for example, or the Yazidis who practice an ancient religion distinct from both Islam and Christianity.