Pamela Newkirk is a professor of journalism at New York University and the author of “Spectacle: The Astonishing Life of Ota benga.”

In the 1920s, the Ku Klux Klan experienced a resurgence fueled by the grievances of white populists, conspiracy theories, fake news, skepticism of science, and hostility toward Jews, immigrants and racial minorities. During that decade, the hooded and cloaked white-supremacist group became as popular as Fourth of July picnics across mainstream America.

In “The Second Coming of the KKK,” two-time Bancroft Prize-winning historian Linda Gordon tells this illuminating and timely tale with meticulous research, tracing the KKK’s tentacles across the country, particularly in the North, where it boasted hundreds of thousands of members. Upending prevalent notions that the Klan was a marginalized group of backward, uneducated Southerners, Gordon notes that between 1915 and 1930 half of the Klan’s members lived in cities, with at least 50,000 in Chicago, 38,000 in Indianapolis and 35,000 in Philadelphia.

While the original Klan of the 1860s was shrouded in secrecy, the 1920s Klan built a prestigious public profile crafted by a professional public relations firm. The KKK advertised in the mass media, sponsored sports teams and college fraternities, held pageants, and, in what Gordon likens to a Ponzi scheme, paid 40 percent commissions to its many recruiters.

“The Second Coming of the KKK,” by Linda Gordon (Liveright)

And unlike the post-Civil War Klan that largely targeted African Americans for lynching and terror, the second Klan gained in number and strength by adding to its list of targets Catholics, Jews, and immigrants from “non-Nordic” and non-Protestant European countries, including Italians and Greeks. Gordon shows that the Klan metastasized in mainstream America by tapping into already dominant views on race and eugenics espoused in leading universities, grade school textbooks and government policies, and by presidents including Theodore Roosevelt.

While the first Klan was a backlash to emancipation and Reconstruction, the second was partly sparked by the 1915 film “Birth of a Nation,” which depicted Klansmen as noble warriors protecting the sanctity of white womanhood from purportedly lustful African American men. The film was screened in the White House and lavishly praised by President Woodrow Wilson, who characterized it as “writing history with lightning” while lamenting, “My only regret is that it is all so terribly true.”

Five years later came “Protocols of the Elders of Zion,” a book published by Henry Ford that was falsely alleged to be the minutes of a late-19th-century meeting of Jewish leaders discussing their plan for domination of global finances and the press. Ford distributed a half-million copies and later published articles in the Dearborn Independent that made many of the same baseless claims.

The Klan routinely circulated fake news about its adversaries in speeches and articles. Catholics — derided as “crossbacks” — were deemed disloyal to America, and the Vatican was falsely accused of plotting a Catholic takeover of the country. Fabricated exposés of escaped nuns and Vatican sweatshops, and of women kidnapped by Jews to work in white slave dens, were widely circulated in the press.

Gordon catalogues the many contradictions, the hypocrisy and the shady but effective strategies that strikingly mirror the playbook of some in the conservative movement today. Klan leaders championed the common man, but the organization was, first and foremost, a lucrative business with the profits flowing to the top. New members paid high initiation fees and annual dues that brought into the Klan coffers as much as $25 million annually — the equivalent of roughly $342 million today. Klan leaders operated a recording company and a real estate firm, and manufactured authentic Klan apparel. The organization also sold products from life insurance policies to memorabilia, including a “Kluxer’s Knifty Knife” and a ladies’ brooch with a “zircon-studded Fiery Cross.” Ads for the items appeared in newspapers across the country. The Klan also gained ground by recruiting a large number of ministers who brought evangelical fervor to its message of white Protestant superiority. Like the recruiters, they were paid.

“Through amalgamating financial, patriotic, and racist interests, the Klan spread like a prairie fire,” Gordon writes. And while the intellectual elite was scorned, the business elite was held in esteem and encouraged to run for office.

“Its primary adversaries, those responsible for the erosion of American values and the American way of life, were not capitalists or men of significant wealth,” Gordon writes. “Instead the elites it condemned were cosmopolitan, highbrow urbanites, who were often liberals.”

The Klan was the first national organization to deny evolution, and it effectively cast its members as victims in their own land. Today’s “Make America Great Again” slogan evokes the appeals of Imperial Wizard Hiram Evans, who said: “We are demanding . . . a return of power into the hands of the everyday, not highly cultured, not overly intellectualized, but entirely unspoiled and not de-Americanized, average citizen of the old stock.”

To bolster its prestige, the Klan exaggerated its size, with an Indiana Grand Dragon claiming to have a quarter-million members — roughly a third of the state’s white male population. A Klan publication announced a parade of 50,000 that was actually attended by only 2,700. “Creating the impression of huge size and unstoppable forward progress, the myth of the Klan as destiny contributed as much as any other tactic to the Ku Klux Klan’s great temporary success,” Gordon writes.

Part cautionary tale, part exposé, “The Second Coming of the KKK” illustrates how a potent and unyielding undercurrent in American life was methodically aroused and unleashed. By following a thread that courses through history, Gordon reveals why a dangerous movement, disdained and underestimated by some intellectual elites, powerfully appealed to a wide swath of white America.

The Second Coming of the KKK
The Ku Klux Klan of the 1920s and the American Political Tradition

By Linda Gordon

Liveright. 272 pp. $27.95