Bingo.
I've been saying similar stuff now for over 5 years on FR -- although not targeting only Christians.
When I've given various "multi-point" considerations why we shouldn't be supporting Romney...This is what I was saying five years ago:
Point 1: This would open the door wide open for the massive LDS public relations propaganda campaign. (This especially applies to POTUS and may or may not apply to all political races): Bill Clinton was a presidential role-model disaster for our young generation re: the scandal. Any president the voting block elevates to the highest role model position in our land accords the highest vote of respectability to the public aspects of what that person stands for. If that person, for example, is a neatly tucked-away communist who's adopted a mask of "family values," & we elect him president, we are telling our kids that communism is OK to emulate. Furthermore, we are handing proselytizing fuel to communists everywhere. It would fuel their door-to-door boldness and other aggressive campaigns to be able to say, "See. Our respectable Communist leader holds the highest office in the land. Come study what helped make the man he is today!"
Obviously, this article also takes in the necessary polytheism and deception of Mormonism.
Why should I heed your advice rather than heeding the words of the Constitution of the United States?
Article VI - Debts, Supremacy, Oaths
The Senators and Representatives before mentioned, and the Members of the several State Legislatures, and all executive and judicial Officers, both of the United States and of the several States, shall be bound by Oath or Affirmation, to support this Constitution; but no religious Test shall ever be required as a Qualification to any Office or public Trust under the United States.