Colin Woodard is the author of five books, including “American Character: A History of the Epic Struggle Between Individual Liberty and the Common Good.” He is a staff writer at Maine’s Portland Press Herald.

One of the great paradoxes of the 2016 presidential election was the overwhelming support of white evangelical Christians for Donald Trump, a vulgar, thrice-married man who bragged of serial sexual assault and whose familiarity with scripture seemed fleeting. Exit polls indicated that 8o percent of them backed Trump, two percentage points more than went for Mitt Romney in 2012 or George W. Bush in 2004. Given that they made up 26 percent of the electorate, one could say their role was decisive. But what accounts for their enthusiasm?

Pulitzer Prize-winning historian Frances FitzGerald’s sprawling new history of the white evangelical movement and its effort to shape the nation is a good place to start looking for answers. For while “The Evangelicals” was completed before the general election, it takes readers from the First Great Awakening of the 1730s to the aftermath of last year’s Republican convention, when it was already clear that the evangelical community was lining up behind the man with the golden Gotham tower. The revealed history suggests that Trump’s campaign rhetoric struck many chords with a movement that’s waged war against cultural pluralism, religious diversity, the Islamic “threat” and the Enlightenment’s very insistence that verifiable facts trump the beliefs they contradict.

FitzGerald shows how a movement that began in reaction to the Calvinist establishment of New England and interior Pennsylvania came to profoundly shape American life and identity in the first decades of the 19th century. It “created a marketplace of religion,” she writes, in which many of the movement’s leaders “explicitly preached individual freedom, the separation of church and state, voluntary association as a primary means of social organization, and republicanism as the best form of government.”

"The Evangelicals: The Struggle to Shape America," by Frances FitzGerald (Simon & Schuster)

But the evangelical world was split by slavery and the Civil War, with Southerners breaking off to form their own slavery-endorsing denominations. In the North, there was a further split when their traditional worldview — that the Bible was inerrant and literally true, and that individual salvation would solve social problems — was challenged by industrialization, the scientific revolution generally, and Charles Darwin and German biblical scholarship in particular, which showed how the Good Book had evolved into its present form. There was an acrimonious struggle between the modernists or liberals who accepted and accommodated these discoveries and the conservatives or fundamentalists who rejected them.

Fundamentalism’s detractors would later associate it with hillbillies and Southern country folk, but as a political matter, the movement was born and based in Northern cities into the 1950s. “By all evidence its main constituency was small-town Protestants who had come to the cities to work in the factories and mills,” FitzGerald notes, where they “found themselves in a pluralistic society where their beliefs were considered outdated or even bizarre.” They reacted by forming “urban ghettos: church communities in which they could separate themselves from what they considered the corruptions of ‘the world.’ ” Seeing themselves as “the saving remnant and the rightful heirs to American civilization,” they sought not Amish-like separation but to be would-be conquerors of a corrupted nation.

Until the 1960s, there was no such movement in the South because there, evangelicals were dominant and unchallenged. But the civil rights movement, desegregation and the cultural revolution of the “Long Sixties” changed that. During the two decades that followed, a new fundamentalist challenge to American liberalism would be lead by Southern televangelists such as Jerry Falwell, who helped rewrite the 1979 Republican Party platform into what he likened to “the constitution of a fundamentalist Baptist Church,” and Pat Robertson, whose 1988 presidential run was undermined by his televised assertions that he could cure the sick and had commanded Hurricane Gloria to spare Virginia Beach. (It devastated Long Island instead.)

Both men allied with Republican presidents and congressional leaders to push laissez-faire economic policies and a hard line on the atheistic Soviet Union, but their wholesale embrace of partisan politics was controversial within the evangelical community, in part because their alliances failed to deliver the social and cultural changes they had promised. After Bill Clinton’s 1996 reelection, the movement despaired. It had virtual control over the GOP’s platform, 18 state parties and the selection of vice-presidential candidates, and yet, FitzGerald writes, “after two decades of Christian Right political activity, the public was not more conservative on abortion than it had been before and substantially more liberal on gay rights and women’s roles.” Its strategist, Paul Weyrich, declared: “I believe we have probably lost the culture war.”

Instead, evangelicals found a willing ally in President George W. Bush, who had been born again, spoke their language and relied on their support to win reelection. Motivated by the same-sex-marriage issue, they turned out for Bush in huge numbers in 2004. “The Christian Right had been left for dead, but in just two years its desiccated organizations had revived and swollen like some desert plants after a rain,” FitzGerald writes. “The Democrats had not seen this coming.” Yet, once again, the effort resulted in disappointment: Bush’s second term was marked by military setbacks in Iraq and economic disaster at home, while same-sex marriage would become the law of the land.

Had Trump lost, this history might have ended with the rise of the “new evangelicals,” a reaction to the Christian right’s politicization of the church. Rick Warren, one of their leaders, called for a “second reformation” that would return evangelicals to their 19th-century roots of “compassionate conservatism” on behalf of the poor, sick and dispossessed. “In a sense,” FitzGerald writes, the movement “came full circle, with a return to the reformist imperatives of the antebellum evangelicals.”

But Trump won, and readers will hear his themes throughout fundamentalist and Christian right factions’ histories: a distrust of diversity, immigration and Islam; a belief in majoritarian rule and that the world is in a state of crisis. There’s William Jennings Bryan’s “view that democracy meant popular sovereignty and the absolute right of the majority to rule”; there’s the 1980s scholarship on fundamentalists showing that their biggest difference with theological moderates was a discomfort with “cultural pluralism and . . . change as a fact of life”; there’s the 2007 polling showing that 63 percent of evangelicals saw immigrants as “a threat to U.S. customs and values” and 90 percent favored “forced deportation” for all undocumented immigrants; and in 2002-2003, Falwell said the prophet Muhammad was a terrorist, Robertson declared Muslims “worse than the Nazis,” and the head of the moderate National Association of Evangelicals feared that Muslims were becoming “the modern day equivalent of the Evil Empire.”

FitzGerald, writing after Trump secured the Republican nomination but before he won the presidency, argues that such voices are on the wane, as younger evangelicals are on the whole more sympathetic with the progressives’ embrace of cultural pluralism, acceptance of moral ambiguities and rejection of intolerance. “Millennial churchgoers were far more ready to accept gays, lesbians, and transgender people and, of course, other ethnic minorities than their elders,” she writes. “Evangelicals might continue to vote Republican, but the demographic changes were already registering in major evangelical organizations . . . [which] were taking on more social justice issues.” If so, Trumpism may find decreasing returns at the ballot box from the passage of time alone.

The Evangelicals
The Struggle to Shape America

By Frances FitzGerald

Simon & Schuster. 740 pp. $35