My guess is that it will be much-quoted over the next couple of years, but here is a key part of it as a reminder: "No religious test shall ever be required as a qualification to any office or public trust under the United States."

Article VI – which, of course, pre-dates even the Establishment and Free Exercise clause of the First Amendment - protects the atheist as well as the religiously devout. It neither mandates religious devotion in a candidate nor prohibits religious debate in the public square. As "On Faith's" moderator Jon Meacham says in his book, American Gospel, "The Founders’ decision to nurture a public piety and treat faith as one force among many to be honored, but heeded only in the measure sensible citizens of the day chose to assign it, stands as an epochal accomplishment…."

So what is “appropriate” in terms of religious expression today? While some certainly disagree strongly about what “appropriate” means in this case, I do believe that a broad consensus has evolved since Jefferson pinned human rights on an endowment by a Creator, and described religious freedom as “the most effective anodyne against religious dissension.”

Presidents and aspiring presidents ever since then have been comfortable in embracing the kind of “public religion” that, if not unique to America, is certainly a highly distinguishing characteristic of it. Lincoln may well have perfected non-specific religious references in civic dialogue. Some presidents have settled for a few personal and spontaneous references to God. Others have made religious comment part of their bully pulpit. A few examples of this wide range:

• Harry Truman, right after he learned of Roosevelt’s death in the closing stages of World War 2: “Boys, if you ever pray, pray for me now.”

• John Kennedy: “I believe in an America where religious intolerance may some day end.”

• Ronald Reagan: "The source of our strength in the quest for human freedom is not material, but spiritual…"

I believe that most Americans are not at all uncomfortable with this, any more than they are uncomfortable with “God bless America” at the end of State of the Union addresses. The American people seem to want their presidents to share their values, and they believe religious beliefs are relevant to those values.

Where the American public becomes uncomfortable is when a candidate or president goes beyond those generalized values and begins talking about their personal religious beliefs in a way that sounds like advocacy.

Which takes us to the part of the question about religious rhetoric. We need to be clear about the definition of the term. As the art of persuasive or effective language, religious terms and images are fair game. But the term “rhetoric” can also imply a sense of insincerity. In today's America, politicians can choose to be religious or not. But they can’t choose sincerity. If they choose to express themselves in religious terms, they’d better be walking the talk.