Religious identity played a key role behind President Trump Donald John TrumpSteele Dossier sub-source was subject of FBI counterintelligence probe Pelosi slams Trump executive order on pre-existing conditions: It 'isn't worth the paper it's signed on' Trump 'no longer angry' at Romney because of Supreme Court stance MORE's surprise 2016 victory, according to pollster Dan Cox, research director of the Public Religion Research Institute (PRRI).

“We talk a lot about changing race and ethnicity but we don’t talk as much about the changing religious landscape as well,” Cox said during a Friday episode of “What America’s Thinking,” Hill.TV’s show about public opinion and polling.

“If you look at the percent of white Christians in the country, it’s declining precipitously, and that’s another part of the story,” Cox said.

He continued: “This sort of fear of tectonic changes that are occurring, that are roiling our political environment, and I think that is what has people up in arms. If you look at what animated voters to Trump, particularly among white, working class, it was these cultural concerns, much more than the economic.”

During his 2016 presidential campaign, Trump repeatedly referred to Christians as being subject to persecution within the United States. He also spoke frequently about uniting Christians against other religious groups.

"Christianity, it's under siege," the future president said during a January 2016 address to Liberty University, an evangelical college overseen by Jerry Falwell Jr. "We've got to protect because bad things are happening, very bad things are happening."

In a research paper published in the May issue of the academic journal Sociology of Religion, a team lead by Clemson University assistant professor Andrew Whitehead found that a perception of America as a Christian nation under attack by secular forces was the greatest predictor of whether a person voted for Trump in 2016 and higher than attitudes about race, immigration, or economic status.

The study also found that people advocating “Christian nationalist” attitudes cared more about their political goals than whether potential allies, such as Trump, actually shared their religious beliefs.

A PRRI report published last year found that 79 percent of white working-class Protestant evangelicals surveyed were afraid the U.S. was losing its cultural identity. By comparison, just 56 percent of white working-class respondents with no religious affiliation agreed.

—Matthew Sheffield