Of course, the speech will be compared to John F. Kennedy's speech, 47 years ago, addressing concerns about his Catholicism. (You can watch and read the speech here.) Kennedy explained, "I believe in an America where the separation of church and state is absolute. . . . I believe in a President whose views on religion are his own private affair, neither imposed upon him by the nation, nor imposed by the nation upon him as a condition to holding that office." As Yuval Levin writes,
Romney seems to have a more complicated challenge: he needs to persuade people who believe a man’s religious convictions do and should make a difference in the sort of leadership he offers that his convictions are like their convictions.
Among other things, the decision to do this suggests the Romney team is finding what a couple of other Republican campaigns have hinted at about the fine details of their Iowa polling: that Romney's slip in Iowa, and Huckabee's rise, has to do with an implicit but very real unease about his Mormonism among evangelical protestants who might otherwise be inclined to support him.