"Almost 50 years ago another candidate from Massachusetts explained that he was an American running for president, not a Catholic running for president. Like him, I am an American running for president. I do not define my candidacy by my religion. A person should not be elected because of his faith nor should he be rejected because of his faith.
Let me assure you that no authorities of my church, or of any other church for that matter, will ever exert influence on presidential decisions. Their authority is theirs, within the province of church affairs, and it ends where the affairs of the nation begin.
As governor, I tried to do the right as best I knew it, serving the law and answering to the Constitution. I did not confuse the particular teachings of my church with the obligations of the office and of the Constitution - and of course, I would not do so as President. I will put no doctrine of any church above the plain duties of the office and the sovereign authority of the law.
As a young man, Lincoln described what he called America 's 'political religion' - the commitment to defend the rule of law and the Constitution. When I place my hand on the Bible and take the oath of office, that oath becomes my highest promise to God. If I am fortunate to become your president, I will serve no one religion, no one group, no one cause, and no one interest. A President must serve only the common cause of the people of the United States ."
-Presidential Candidate Mitt Romney on "Faith in America"
...which is why I find it incredibly difficult to imagine that a Christian can be president.