Democrats are saying that religious conservatives are too powerful inside the Republican Party. Republicans are saying that the Democrats are hostile to religious values. Liberals worry that religious themes are too prominent in the nation’s civic life. Conservatives are troubled that the nation has come unmoored from its values.

We’re fighting about religion again. We’re fighting about how much religion in the public square is appropriate, about whether religion belongs in the schools, about the place faith has in our politics. We’re doing one thing more: We’re saying that we’ve never fought this much about religion.

But as bitter as this fight is, as wrenching as the questions seem, as high as the stakes are, the truth is that this tension over the role of religion is one of the great constants in American life. In fact, religion often appears at times of national stress. Just as it often brings enormous comfort in the personal lives of Americans, it often prompts enormous uneasiness in the political life of the nation.

Historians are still debating how important a factor was the Great Awakening in pushing Americans toward revolution in the late 18th century. The Civil War was preceded by deep religious awakenings. The industrial revolution and the civil rights movement also were accompanied by huge upsurges in the role of religion in American life.

Indeed, the struggle between the religious and the secular is one of the defining elements of American civic life. “American culture has lodged at its heart a large chunk of religiosity,” says Allen C. Guelzo, a Gettysburg College historian. “The American character has two twins, like Jacob and Esau, each struggling for superiority.”

These are legacies of the twin wellsprings of our nation, the Enlightenment (as personified by Benjamin Franklin) and the Great Awakening (as personified by Jonathan Edwards).

But there are times when the secular and the religious are so intertwined that it is difficult to sort one from the other. In his second inaugural address, perhaps the finest speech ever delivered by an American president, Lincoln expresses his frustration over the unresolved conflict of the Civil War, saying, “The Almighty has his own purposes.” In the very next sentence, he cites the Gospel according to Matthew and concludes the paragraph by quoting from the Psalms, “The judgments of the Lord are true and righteous altogether.”

A century later, the struggle for black social, economic and political rights was rooted in religious institutions. Many of the leaders of the civil rights movement, including the Rev. Martin Luther King Jr., were ministers. They were assisted by a cadre of priests and rabbis. The soundtrack of the movement – and the best example comes from King’s speech during the 1963 March on Washington – came from the pulpit and from Negro spirituals.

In our own time, religious elements are unavoidable in the political world. But that is not a new development. Evangelicals, for example, have been an important force in American politics since before the Revolution. “The success of the Revolution, and the exhilarating prospects that it aroused, inspired a new generation of respectable evangelicals to reshape the social landscape of the United States,” the Princeton historian John M. Murrin has written. “Far more dramatically than their predecessors of 1740, they imposed their social vision upon their fellow citizens until their reformist ardor drove an angry South to secession.”

In the next century, evangelicals were part of the New Deal coalition, and then, playing the opposite role in the political arena, they were part of the Reagan coalition. More than three Americans in five say they pray every day, according to a Newsweek/ Beliefnet poll taken this summer. But the percentage of Americans who say they attend worship services every week hasn’t changed in four decades. It was 44 percent in a Gallup Poll in 1966, and it was 45 percent in the Newsweek/Beliefnet poll in 2005.

It has become customary to argue that religion is a far more visible part of American civic life than it has been in our lifetimes. In some ways that is true: President Reagan was the beneficiary of evangelicals’ support, and he provided great inspiration to evangelicals, but he was not one of them.

President Bush is the beneficiary, inspiration and personification of religious conservatism today. President Reagan spoke about religious values, but at base what he really believed in was the abiding power of the American spirit. President Bush speaks about American values, but at base what he really believes is the abiding power of spirit and God to redeem America.

But it may be too much to argue that the Bush ascendancy represents the triumph of religion in American politics. Despite the importunings of philosophers like W.E.B. DuBois and artists like Paul Robeson, the civil rights movement was drenched in the spirit of religion. Jimmy Carter spoke openly about his personal relationship with God in the 1976 campaign and throughout a presidency in which he prided himself in teaching Sunday school. The Rev. Pat Robertson ran for president in 1988, came in second in the Iowa caucuses that February and took 14 counties. (A dozen years later, Gov. George W. Bush, of Texas, took 13 of those counties.) Bill Clinton’s speech beat to the rhythms of the rural Arkansas gospel sing.

Even so, religious conservatives still worry that the nation is more rootless and godless than ever, even as liberals worry that the line between the pulpit and politics is getting blurred as it never has. The truth is that Americans have always been rootless and that the line between church and state has always been a smudge.

So, too, is the line between religious conservatives and social liberals. An essay by Doug Muder in UU World, the magazine of the Unitarian Universalist Assn., makes a telling point. “In fact, religious conservatives and liberals share more concerns and beliefs than either commonly admits,” he writes. “Both have loyalties that go beyond self and the convenience of the moment. Both reject the materialism of popular culture. Both seek something more substantial than the momentary satisfaction of desire or the endless striving after status.” They agree on so much. Note, however, that they do not agree on the role of religion in civic society. They almost never have.

– David Shribman is executive editor of the Pittsburgh Post-Gazette.