The second part of the first amendment requires separation of church and state, and elsewhere, the Constitution requires that there be no religious test for office. Ben Carson requires that there be a religious test for office. This is because Carson is, essentially, an Evangelical Christian, in the sense that he believes, as do many other Gops, that Christian belief and doctrine should be part of our governance and law.
In other words, Carson believes first in a higher power, God, to whom he owes primary allegiance and, critically, believes that the belief system that emerges from worship of that god should guide his actions and, if he is elected, governance. In other words, he is not inclined to separate his religious life from his job. But, if elected, he would take an oath to the US Constitution. By taking this oath with the equivalent of sworn belief to a different authority, his very first act of being president, the actual act of becoming president himself, will be an act of treason. You might as well just set up the impeachment proceedings in advance and get it over with.