A new documentary examines how rising white Christian nationalism in the U.S. could upend democracy and impose theocratic rule at a time when the nation is becoming more diverse and less religious.

Why it matters: "God & Country," set to be released in select theaters Friday, arrives as books published recently by former and practicing evangelicals have issued alarms about the Christian nationalism that has increased its presence in churches and Republican politics.

• The film, produced by Rob Reiner, follows the rise of white Christian nationalism, from its role in fighting racial desegregation in the 1950s to its influence on the Jan. 6 insurrection in 2021.

Zoom in: The left-leaning Reiner, who directed "When Harry Met Sally" and "The Princess Bride," recently co-hosted new 10-part podcast series called "Who Killed JFK?"

• Through interviews with white and Black evangelicals, religious leaders and scholars, the new documentary portrays how a once-fringe part of the evangelical movement became a dominant force in right-wing Christian circles.
• The film describes how the movement's increasing popularity bled into the nation's politics and helped fuel the election of Donald Trump — a New York real estate mogul who had little connection to Christianity or the evangelical movement before he ran for president.

Among those interviewed are Charlie Sykes of The Bulwark, a conservative anti-Trump website, and Russell Moore, a theologian who resigned from the Southern Baptist Convention amid a backlash over his criticism of Trump.

• Also interviewed are the Rev. William Barber, a significant figure on the Christian left, and former far-right evangelical leader Rob Schenck.
• They speak of how the Christian nationalist movement drove a rise in megachurches whose leaders preached a form of white nationalism while decrying civil rights and LGBTQ+ people.

The intrigue: The film includes footage of rallies where attendees wave Christian nationalist and Confederate flags, and sound bites of Christian leaders denouncing diversity programs and immigrants.

What they're saying: "I just could not believe the size and the scale of what was going on out there," Dan Partland, the film's director tells Axios.

• Partland said he was inspired to dive into the project after reading Katherine Stewart's 2020 book, "The Power Worshippers: Inside the Dangerous Rise of Religious Nationalism."
• He later recognized images of Christian nationalism on flags and slogans during the Jan. 6 insurrection.

Jemar Tisby, CEO of the Black Christian Collective called "The Witness," talks in the film about becoming Born Again as a teenager and being educated in white evangelical circles.

• "When I started critiquing Donald Trump's racist rhetoric, I got a level of vitriol and pushback from evangelicals that I hadn't even seen," he tells Axios.
• He also realized that white evangelicals often refused to talk about race and social justice, dismissing those who wanted to discuss those issues as "woke."