There was a flurry of correspondence with the Anti-Defamation League in the wake of his statments. (reprinted below) But the upshot was this statement from the ADL:

In response, ADL welcomed Sen. McCain's clarification, but added, "Nevertheless, we are deeply disappointed that you did not expressly retract your statement that "the Constitution established the United States of America as a Christian nation.

Last October, journalist Dan Gilgoff interviewed John McCain on BeliefNet. The interview was  titled:  John McCain: Constitution Established a "Christian Nation."

Q: A recent poll found that 55 percent of Americans believe the U.S. Constitution establishes a Christian nation. What do you think?

McCain: I would probably have to say yes, that the Constitution established the United States of America as a Christian nation. But I say that in the broadest sense. The lady that holds her lamp beside the golden door doesn't say, "I only welcome Christians." We welcome the poor, the tired, the huddled masses. But when they come here they know that they are in a nation founded on Christian principles.

Abraham Foxman, ADL National Director wrote to McCain about this  on October 1, 2007. McCain replied, and the ADL rejoined.

We write in response to your recent interview posted on Beliefnet.com. We and others are confused and dismayed by the comments you made in the course of this interview. On the one hand, you correctly noted that our Founding Fathers unequivocally believed in the separation of church and state. Yet you then came to the conclusion that "the Constitution established the United States of America as a Christian nation."

While this view may reflect what recent polls show is the opinion shared by a majority of Americans today, it is false. Absolutely nothing in the Constitution establishes that the U.S. is a Christian nation, nor is it accurate to say that this nation was founded on Christian principles.

The sources that influence the framers ranged from Greek and Roman law, to John Locke, to Scottish Common Sense philosophers to Calvinism. The Founding Fathers actually rejected attempts to include Biblical passages and religious principles in the Constitution. In fact, every attempt to include official recognition of Christianity in the United States Constitution was defeated. The secular character of the new nation was affirmed in the Treaty of Tripoli (1797) which was negotiated under George Washington and signed by John Adams: "The Government of the United States is not, in any sense, founded on the Christian religion."

We were pleased that you clarified your earlier remarks about Muslims' suitability to serve as president, and made it clear that you would be willing to vote for a Muslim candidate. As you well know, our Constitution explicitly states that "no religious test shall ever be required as a qualification to any office or public trust under the United States."

While the Anti-Defamation League is non-partisan and does not endorse or oppose any candidate for office, we believe deeply that voters should be making their decisions on the basis of a candidate's qualifications and positions on substantive issues. We do not ask candidates to hide their religious heritage or the impact religion has had on them. But appeals to voters based on religion are inevitably divisive and contrary to the democratic ideals upon which our nation was truly founded.

We urge you to reconsider and withdraw your statements describing the United States as a "Christian nation" and a "nation founded on Christian principles." Not only were your assertions inaccurate, they were also ill-advised for any candidate seeking to lead a nation as religiously diverse and pluralistic as ours.

McCain replied:

You have misconstrued my interview with Beliefnet, in which I made repeated references to the "Judeo-Christian" values that informed our founding fathers' respect for human rights. I did not assert that members of one faith have a greater claim to American citizenship than another. In fact, I stressed the opposite, noting that "the lady who holds her lamp beside the golden door doesn't say 'I only welcome Christians.'" Read in context, the interview makes clear that I believe people of all faiths are welcome here and entitled to all the protections of our Constitution, including the unfettered right to practice their religion freely. In the interview, I observed that the values protected by the Constitution - such as respect for human life and dignity - are rooted in the Judeo-Christian tradition. That is all I intended to say to the question: is America a Christian nation?

While I acknowledged that I might be more comfortable voting for someone who shared that tradition, I also made clear that a candidate's faith should not be a barrier to running for or serving in high office. And in a clarification I gave Beliefnet shortly after the interview I said I could support a Muslim candidate for President, if I believed he or she were the best qualified to serve in that capacity.

I hope you will now see that your concern was misplaced. I have always made it a practice to put the country's best interests before my own, and have always avoided seeking political gain by aggravating racial or religious divisions among us, and I regret the insinuation that I would. Indeed, I do not think you can find anything in my life and political record to suggest the contrary. I was asserting nothing more controversial than that I recognize the human rights cherished in America, which the Constitution was conceived to protect, and which Americans have sacrificed their lives to defend, are values cherished in Judeo-Christian tradition.

Foxman rejoined:

Thank you for your quick response to my letter expressing concern over your interview with Beliefnet in which you referred to the United States as a "Christian nation."

We welcome your clarification that you were "asserting nothing more controversial than that you recognize the human rights cherished in America.....are values cherished in the Judeo-Christian tradition."
Nevertheless, we are disappointed that you did not expressly retract your statement that "the Constitution established the United States of America as a Christian nation." Unfortunately, that phrase is often exploited by those who do not fully appreciate the importance of our Constitution's guarantee of religious freedom and equality which you embrace.

We hope that you will express your commitment to our pluralistic values in more inclusive language in the future.

Here is the ADL press release on the flap.

The blog Jed Report made a You Tube video from an interview conducted by Dan Gilgoff at Beliefnet last year. It is a compelling two and a half minute bit of vid, but Jed Report does not identify the source. The link to the original is in this post.

A hat tip and a sweeping bow to Daily Kos diarist DrSteveB for originally flagging this in response to the Obama/Farrakhan episode.

For a primer on Christian nationalism, see: History is Powerful: Why the Christian Right Distorts History and Why it Matters.