One of the best questions in the Republican debate at Jacksonville will prove, we predict, to be the question about religious faith, and the best answer was the one of Senator Santorum. Ira Stoll at futureofcapitalism.com has a similar reaction. The question had been put by a local lawyer, Suzanne Bass. “How,” she asked, “would your religious beliefs, if you’re elected, impact the decisions that you make in the office of the presidency?”

All four gave terrific answers. Congressman Ron Paul said “my religious beliefs wouldn’t affect it . . . the only thing that would affect me in the way I operate as a president or a congressman is my oath of office and my promises that I’ve made to the people.” Governor Romney acknowledged Dr. Paul’s point, but went on to speak of how “ours is a nation which is based upon Judeo- Christian values and ethics.”

Mr. Romney also brought up the Independence Declaration as “something which described the relationship between God and man . . . So when they said, for instance, that the creator had ‘endowed us with certain unalienable rights, among them life, liberty and the pursuit of happiness,’ I would seek to assure that those principles and values remain in America and that we help share them with other people in the world.”

The former speaker, Newt Gingrich, said he agreed with Mr. Romney and added that “anyone who is president is faced with decisions so enormous that they should go to God.” He also talked about “an increasingly aggressive war against religion and in particular against Christianity in this country, largely by. . .” he was interrupted by applause “largely by a secular elite and the academic news media and judicial areas. And I frankly believe it’s important to have some leadership that stands up and says, enough.”

But it was really Mr. Santorum who most clearly explicated the civics lesson. “Faith is a very, very important part of my life,” he said, “but it’s a very, very important part of this country. The foundational documents of our country. Everybody talks about the Constitution, very, very important. But the Constitution is the ‘how’ of America. It’s the operator’s manual. The ‘why’ of America, who we are as a people, is in the Declaration of Independence.”

He then quoted the endowment clause of the Declaration — “all men are created equal and endowed by their creator with certain inalienable rights” — and asserted that the Constitution is there to do but one thing, protect God-given rights. He asserted that’s what makes America different. And then the great point: “So when you say, well, faith has nothing to do with it, faith has everything to do with it. If rights come . . . If our president believes that rights come to us from the state, everything government gives you, it can take away.”

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Mr. Santorum was speaking at a moment when the struggle over religious freedom in this country is being joined. It is an enormous sleeper of an issue, in our estimation, and an understanding of the fundamentals of freedom in our constitutional democracy is going to be essential. The sentiment that Mr. Santorum expressed so clearly is grounded not only in our Constitution but in what might be called supra-constitutional sentiments. It was Geo. Washington himself, in his Farewell Address, who issued the most famous formulation, warning:

“Let us with caution indulge the supposition that morality can be maintained without religion. Whatever may be conceded to the influence of refined education on minds of peculiar structure, reason and experience both forbid us to expect that national morality can prevail in exclusion of religious principle.”

The Supreme Court just turned back an attempt by the Obama administration to override religious principle the Hosanna-Tabor Evangelical Church, in Michigan, was trying to assert in the hiring of a minister. The court’s decision, which was nine to zero in favor of the church, bodes well for the religious side of this vast struggle. Experience tells us, though, that it’s going to be a long one, as the state seeks to exclude religious principle in same-gender marriage cases, abortion cases, and zoning battles. It’s a context in which it was just wonderful to hear a candidate like Mr. Santorum put the basics in such clear language.