You'll often hear that when George Romney, Mitt's father, was contemplating a presidential run, almost nobody cared about his Mormonism - which shows how far we've fallen from the ideal of church-state separation. Except that public opinion hasn't really changed between then and now:
As far back as 1967, only three-quarters of Americans said they would vote for an otherwise well qualified person who was a Mormon. This year – some 40 years later -- the results to this question are almost exactly the same.
[George Romney] did face this problem, but failed to gain any ground as a presidential candidate before there was that much time for the issue to become a prominent one. We may forget, as we now enter the eleventh month of this election campaign (11 down, 11 to go!), that Romney started his campaign for the Republican nomination in November 1967 and by the end of February he was out. He was a declared candidate for a little over four months. He had made his famous “brainwashed” remark earlier in 1967 before becoming an avowedly antiwar candidate (an example his son has definitely not followed). His son started organising the preliminary elements of his presidential campaign in 2005, and there has been active speculation about his presidential run since mid-2006 at least. There has been much more time to ponder the implications of this factor, much more time to do a lot of polling on it, and much more time for pundits and bloggers to write endless commentaries on the topic.
The issue has taken on added significance in the nominating contest because evangelicals, many of whom would have been Democratic voters in 1967-68, have since started voting Republican much more frequently. As a Republican candidate before the 1968 realignment, Romney would have been more insulated from the early pressures his son is now experiencing. Had he been a Democrat, the issue might have become more significant in the nominating contest.
I would only add that a lot of people are confused about why religious issues appeared to be less salient in the politics of 1950s and 1960s.
It is true that the secular nature of postwar U.S. politics was not the historical rule. It was progress: The America of the nineteenth and early twentieth centuries was a less hospitable place for religious minorities. The temperance crusaders and the populists, for instance, were religiously steeped mass movements with more than a whiff of, respectively, anti-Catholicism and anti-Semitism. The secularism that has generally prevailed since World War II is precisely what has allowed a Catholic to be elected president and a Jew to be nominated as vice president, among other ways that religious tolerance has expanded.
But this “progress” wasn’t the result of people waking up one day and deciding they should leave religion out of politics; it was the result of sociological trends that were unique in American history, and couldn't possibly be expected to endure. Thirty years of immigration restrictions; the rise of a mass-market media with a commercial interest in being as inoffensive as possible; the homogenizing impact of large-scale federal mobilization, first in the New Deal and then in WWII and Korea; the withdrawal of America’s evangelicals from political activism; and the absence of the “personal-is-political” divisions opened by the Sexual Revolutions – all of these factors and more made the ecumenical “Protestant-Catholic-Jew” landscape of the ‘50s and ‘60s possible, in the same way that they helped create the larger “end of ideology” moment in American politics as a whole. (It’s easy to be tolerant and anti-ideological when everybody increasingly looks and sounds and even thinks the same; it’s easy to embrace a “secular” politics when religious divisions seem to be steadily narrowing to the point of unimportance.)
But these homogenizing trends didn't last, and I’m pretty sure that most of the people who pine for the “secular politics” of the Fifties wouldn’t want them to have lasted. America is a more diverse country than it was in 1960; its cultural landscape is more varied and more fragmented; there’s no WPA and no draft; evangelicals are back in the political arena; and the debates over feminism, abortion and gay rights have opened up political and theological divisions between faiths, and within them, that simply didn’t exist when JFK ran for President. Which is to say that the United States has become, well, normal again: It's the homogenization that held sway in the mid-century period that was exceptional and unsustainable; our diversity, and the religious and ideological feuding that goes along with it, is what's to be expected of life in a mass democracy.