It’s in classrooms, some of which teach creationism. The Texas Board of Education has been withholding approval of a widely used biology textbook because it presents evolution as more than just a theory. Thus, in the nation’s second most populous state, whose governor essentially kicked off his 2012 presidential campaign with a stadium rally for tens of thousands of evangelicals, religion is trumping scholarship, at least for now.

“So help me God.” “Under God.” “In God We Trust.” Perhaps we’re meant to register these ubiquitous phrases as unspecific inspirations, vague recognitions of an undefined higher power, general appeals to generous living. But they’re rooted in a given religious tradition and are arguably the gateways to the Arkansas ridiculousness and to the overwrought accusations of a “war on Christmas” that herald the holiday season as surely as Frosty the Snowman and Black Friday do.

Three of four Americans are at least nominally Christian. But that leaves one in four who aren’t. One in five Americans don’t claim any binding religious preference or affiliation, and their ranks have grown significantly over the last two decades. Out-and-out atheists remain a sliver of the population, but a restive sliver at that. On some Sundays in some cities over recent months, they’ve gathered by the hundreds for church-style celebrations without psalms, making the point that good will and community don’t depend on divinity.

The centrality of religion in this country’s birth and story can’t be denied. And shouldn’t be. And having the Bible at inaugurations honors tradition more than it offends pluralism. But using the Bible as a litmus test for character betrays the principles of religious liberty and personal freedom, along with the embrace of diversity, that are equally crucial to America’s identity and strength. It also defies the wisdom of experience. How many self-anointed saints have been shown not to practice what they preach? How many of the ostentatiously faithful have fallen? Theirs is an easy pose, and sometimes an empty one.

The intrusion of religion into campaigns gets ugly. During both of Barack Obama’s presidential bids and over the years in between, his enemies tarred him with what they clearly saw as the most damning accusation of all: He’s not Christian! The same kind of charge was infamously hurled at Kay Hagan, a North Carolina Democrat, on the road to her election to the Senate in 2008. Her opponent, Elizabeth Dole, ran a commercial that showed Hagan’s face while a voice — not Hagan’s, though viewers could easily have thought it was — said, “There is no God.”

So did Hagan denounce this as a wrongful commingling of piety and politics? No, she labeled it defamatory, saying in a commercial of her own that it was an example of “bearing false witness against fellow Christians.”