In 2009, the gap between the share of Republicans and Democrats who believed in evolution was just 10 percentage points, 54 percent and 64 percent, respectively.

Last year, that gap widened to a whopping 24 points because as the percentage of Democrats who believed in evolution inched up to 67 percent, the percentage of Republicans believing so plummeted to 43 percent. Now, more Republicans believe that “humans and other living things have existed in their present form since the beginning of time” than believe in evolution.

This sad news comes via a survey released this week by the Pew Research Center’s Religion & Public Life Project.

In fact, this isn’t only sad; it’s embarrassing.

I don’t personally have a problem with religious faith, even in the extreme, as long as it doesn’t supersede science and it’s not used to impose outdated mores on others.

But some people see our extreme religiosity itself as a form of dysfunction. In a 2009 paper in the journal Evolutionary Psychology, Gregory Paul, an independent researcher, put it this way: “The level of relative and absolute societal pathology in the United States is often so severe that it is repeatedly an outlier that strongly reinforces the correlation between high levels of poor societal conditions and popular religiosity.”

But I believe that something else is also at play here, something more cynical. I believe this is a natural result of a long-running ploy by Republican party leaders to play on the most base convictions of conservative voters in order to solidify their support. Convince people that they’re fighting a religious war for religious freedom, a war in which passion and devotion are one’s weapons against doubt and confusion, and you make loyal soldiers.

There has been anti-science propagandizing running unchecked on the right for years, from anti-gay-equality misinformation to climate change denials.

When you look at white evangelical Protestants, the evolution denialism gets even worse. Only 27 percent of that group believes in evolution. According to a 2011 Pew report, while white evangelical Protestants make up only 18 percent of the population overall, they “make up 43 percent of Republicans who fall into the category of staunch conservatives.”

Pew defines “staunch conservatives” as those who “take extremely conservative positions on nearly all issues — on the size and role of government, on economics, foreign policy, social issues and moral concerns. Most agree with the Tea Party, and even more very strongly disapprove of Barack Obama’s job performance.”

Pew found that most staunch conservatives were regular viewers of Fox News, preferring the network to any other news source.

Fox has helped to ingrain the idea that Republicanism and religiosity are embattled and oppressed, fighting for survival against the forces of secular extremists.

There was, for instance, the Fox News-fabricated “War on Christmas” and its fight against the “Happy Holidays Syndrome.”

The face of the network’s defense-of-Christmas crusade has been the “Killing Jesus” co-author Bill O’Reilly, who this season declared a victory. In December, he said on his show: “It isn’t a mythical war on Christmas. It’s real, and we just won.”

But Fox is not alone. The Christians-on-the-defensive stance was front and center in the 2012 Republican presidential primaries. During a debate in January of that year, this question from a Virginia man was put to the candidates: “Given that you oppose gay marriage, what do you want gay people to do who want to form loving, committed, long-term relationships? What is your solution?”

Newt Gingrich responded, in part citing “secular bigotry”: “The bigotry question goes both ways, and there’s a lot more anti-Christian bigotry today than there is concern on the other side, and none of it gets covered by the news media.”

There was a sustained round of applause for Gingrich’s statement. So of course, the eventual nominee, the self-proclaimed “severely conservative” eater of “cheesy grits” Mitt Romney, had to ride Gingrich’s coattails by chiming in, “As you can tell, the people in this room feel that Speaker Gingrich is absolutely right, and I do too.”

Last year, the Liberty Institute and the Family Research Council released an updated, 189-page version of a book called “Undeniable: The Survey of Hostility to Religion in America.”

This is a tactic to keep the Republican rank-and-file riled up, to divert their attention from areas of common sense and the common good. After all, infidels are deserving of your enmity, not your empathy.