The separation of church and state is a long held American belief, and one which the founding fathers were careful to put into the Bill of Rights. However, there have always been people who have pushed against that barrier, or who have been afraid that other people might push against it. John Kennedy, the first Catholic president that we’d had, was one example. Some Americans were convinced that, as a Catholic, Kennedy would simply follow the directives of the pope when governing the country. So Kennedy made a statement that has rung throughout the years, explaining how a man in power must separate his religious beliefs from his duties and responsibilities to the country whose care he’s been given.This/tag helps explain it more.
Kennedy explained very simply that you cannot judge policy based simply on your religion. That you must do what is right for the people, and for all the people, without infringing on any of their rights. This statement, which was common sense when Kennedy made it, has been railed against in recent politics by the Christian Right, and by politicians like Rick Santorum whose views have come full circle to be against the sort of separation that Kennedy so heartily espoused.