There is no record that political pollsters in ancient Rome even knew that Jesus of Nazareth told a Jewish leader named Nicodemus that he needed to be "born again" in order see the Kingdom of God.

Germans in the Protestant Reformation embraced that "born again" image and called themselves the "evangelisch." Then in 1807, English poet Robert Southey was one of the first writers to turn the adjective "evangelical" -- think "evangelical" preaching -- into a plural noun "evangelicals." There was no earthquake in European politics.

But America changed forever when Bible Belt Democrat Jimmy Carter shocked journalists by saying that he had been "born again." That firestorm led Newsweek editors to grab a phrase from pollster George Gallup and proclaim 1976 the "Year of the Evangelical." Lots of politicos noticed, including a rising Republican star named Ronald Reagan.

The rest is a long story. 

"The news media and polling agencies realized that the 'born again' vote was a seminal political factor," noted historian Thomas Kidd, in a recent address at Wheaton College, the alma mater of the late evangelist Billy Graham.

"The Gallup organization," he added, "began asking people whether they had been 'born again.' The emergence of EVANGELICAL as a common term in news coverage of politics was a major landmark in the development of the contemporary evangelical crisis. … The media's frequent use of 'born again' and 'evangelical' connected those terms to political behavior."

More some evangelical insiders relished this attention, while denominational leaders and other mainstream evangelicals failed to realize that "they were losing control of the public's perception of their movement," said the scholar from Baylor University.

But one thing would become crystal clear, according to Kidd's new book, "Who is An Evangelical?" His bottom line: "The gospel did not make news. But politics did."

That reality was locked in place when a thrice-married New York billionaire became the latest Republican to grasp that he couldn't reach the White House without a massive "pew gap" between himself and the ever-controversial Hillary Rodham Clinton. Eventually, 81% of white, self-proclaimed "evangelicals" -- many enthusiastically, many reluctantly -- voted for Donald Trump in the 2016 general election.

At that point, said Kidd, the vast, complex, multicultural reality that is the evangelical movement -- both in America and around the world -- was trapped in a stereotype. Evangelicals were no longer "born again" Protestants who "cherish the Bible as the Word of God," while urgently proclaiming salvation through "a personal relationship with Jesus Christ." Evangelicals are now white Republicans who voted for Trump, and that's that.

Forget the historic importance of African-American evangelicals in the Civil Rights era and beyond. Forget the explosive growth and influence of evangelical and Pentecostal Latino churches across America. Forget the rise of church-planters and evangelists from Asia, especially South Korea.

Some journalists and pollsters are now operating on the assumption that white evangelicals are the only evangelicals that matter, noted Kidd, reached by telephone. A few have, however, started to realize that many Americans who self-identify as "evangelicals" are not walking the talk. 

That has been common knowledge since the late 1970s, when Gallup researchers began asking hard questions about religious beliefs and the practice of those beliefs in daily life. Gallup cut its estimate that "evangelicals" were 34% of America's population to 18% -- a number that would shock many journalists, as well as GOP activists.

"Evangelicals are covered, they are important, when they are a factor in politics -- period," said Kidd. "All of those evangelicals who are not even voting, and there are lots of them, may as well not even exist. Their lives, by definition, are not newsworthy."

This national obsession with the clout of the "81 percent" of white evangelicals who voted for Trump may even be causing journalists and pollsters to miss important political stories, especially in rapidly changing states like Florida and Texas.

Right now, said Kidd, Latinos are the "most intriguing evangelicals, to me, because their numbers are growing so fast and their allegiances are totally up for grabs. … If you want to know where evangelicals are going, you have to watch all the independent churches, the storefront churches in big urban areas. Look at the churches that are growing and they are immigrant churches -- all kinds of immigrants."