From Donny and Marie Osmond, to HBO's "Big Love," to Proposition 8 in California, to persistent -- and inaccurate -- Beltway legends about how half of the CIA is staffed by members of the LDS Church, America's Mormons have a way of episodically popping into the national consciousness. The recent ascent of Mitt Romney to the status of presumptive Republican nominee is no exception to this rule. It is yet another "Mormon moment" in a long string of such moments dating back to the 19th century.