This does not mean Romney should quote from the Book of Jarom in his convention speech. It is constitutionally improper for a president (or prospective president) to be sectarian. But it is constitutionally appropriate — and politically advisable for Romney — to tell his whole personal story, which is uninteresting without his faith. Romney needs to tether his character and values to an immovable stake. And he has every cause to praise the generosity of a country where no group need be an "out-group" forever.
In the process, Romney would accomplish for Mormonism what others achieved for Catholicism and Judaism — the incorporation of a new tradition into American civil religion. This does not involve theological acceptance, just a recognition of common values and common citizenship. And it may come easier for Mormonism than many imagine, because no faith is more distinctly American.
Michael Gerson's email address is firstname.lastname@example.org.