“Religion and Christianity are the two biggest things missing from this country,” Donald Trump declared.

Despite (or perhaps because of) the messenger, the argument for Christian nationalism has been amplified in recent years, and Christian nationalism — the fiction that the United States is and always was a Christian nation—is very much on the ballot this year.

Trump’s acolytes, with his encouragement, are pushing to repeal same-sex marriage, to post religious sentiments in public places and use taxpayer money for religious education, a clear violation of the establishment clause of the First Amendment: “Congress shall make no law respecting an establishment of religion.”

Unfortunately, Trump’s Supreme Court, which has scant regard for the First Amendment and the separation of church and state, is complicit. (I wish the current Supreme Court had half as much deference for the First Amendment as it does for the Second Amendment.)

The notion of Christian nationalism is nothing new in American history. At various moments, in perceived times of crisis, Christians have pushed to designate the United States as a Christian nation, despite the First Amendment’s explicit disavowal of religious establishment.

One of the Confederacy’s criticisms of the Union was the lack of Christian language in the Constitution, so the South took pains to declare that the Confederate States of America was a Christian enterprise. This in turn prompted the formation of a group calling itself the National Reform Association (NRA) to propose a constitutional amendment designating the United States as a Christian nation, crediting “the Lord Jesus Christ as the Ruler among the nations.”

The NRA included ministers, seminary professors and William Strong, a justice on the Pennsylvania Supreme Court who was later appointed to the U.S. Supreme Court in 1870 by Ulysses S. Grant. During the Civil War, the NRA took its proposed amendment to the White House, whereupon Abraham Lincoln wisely temporized, averring that “the work of amending the Constitution should not be done hastily.”

Nothing came of the proposal.

In 1947, during the throes of the Cold War, another group called the Christian Amendment Movement proposed a similar amendment in which the nation “devoutly recognizes the authority and law of Jesus Christ, Savior and Ruler of nations, through whom are bestowed the blessings of Almighty God.” Congress refused to pass the measure, but during the Eisenhower administration they did add “under God” to the Pledge of Allegiance and “In God We Trust” to the nation’s currency.

The Supreme Court’s decisions outlawing Bible reading and prescribed prayer in public school in the early 1960s prompted the proposed Becker Amendment to ensure that “prayers may be offered in the course of any program in any public school or other public place in the United States.” The bill died in committee.

The argument that the United States is a Christian nation rests on two faulty premises, bad history and bad theology, but it’s also bad strategy.

Theologically, Jesus himself declared “my kingdom is not of this world,” and after he had fed the five thousand, according to St. John, he suspected that the crowd wanted to crown him king, whereupon he fled into the mountains.

Historically, Christian nationalism relies on the specious claim that the founders were Christians, even evangelical Christians. This is so ludicrous that it barely bears refuting. Suffice it to say that with the (remotely) possible exceptions of John Witherspoon, Presbyterian minister and president of the College of New Jersey (Princeton), and Benjamin Rush, a physician, no founder would qualify for membership in any of the churches now advocating Christian nationalism.

In addition, Article 11 of the Treaty of Tripoli, ratified unanimously by the U.S. Senate on June 7, 1797, reads in part, “As the United States is not in any sense founded on the Christian religion. . . .”

Christian nationalism is bad theology and bad history, but it’s also bad strategy for anyone who cares about faith.

The disestablishment of religion as mandated by the First Amendment set up a free marketplace for religion in the United States. Because the state stayed out of the religion business, religious entrepreneurs (to extend the economic metaphor) have been free to appeal for followers. This has lent an energy and vitality to religion unmatched anywhere in the world.

The First Amendment, America’s best idea, has worked remarkably well for more than two centuries.

As Sandra Day O’Connor wrote in her final church-state decision, “Those who would renegotiate the boundaries between church and state must answer a difficult question: Why would we trade a system that has served us so well for one that has served others so poorly?”

Randall Balmer teaches at Dartmouth College and is the author of “Solemn Reverence: The Separation of Church and State in American Life.”