Commentators who were respected, card-carrying evangelical Protestants as of June 16, 2015 (when Donald Trump announced) are saying their movement faces a “crisis” and its very name should be shelved as too politicized, at least in the U.S. A few celebrities unite with multitudes of grass-roots voters in linking evangelicalism with the Donald Trump-ified Republican Party.

Yet there are many non-partisan leaders like the Rev. Leith Anderson, who’s retiring after 13 years as president of the National Association of Evangelicals (NAE). He tells the savvy Adelle Banks of RNS that “I want the standard to be what the Bible teaches, not what the polls report.”

The media won’t be dumping the E-word any time soon. But amid the confusion and rancor, we do need to know what we’re talking about. Thus the value of the new Eerdmans paperback ”Evangelicals: Who They Have Been, Are Now, and Could Be.” This anthology of old and new articles was compiled by expert historians David Bebbington of Britain and Americans George Marsden and Mark Noll.

Self-identified evangelicals form the largest U.S. religious bloc, and the book has three potential uses for journalists. First, it could focus an analytical article. Second, it offers fine introductory background for writers who are new to this terrain. Third, those who already know a lot will learn some things.

Making definitions difficult, this fluid movement crosses denominational lines and combines formal church bodies, myriad independent congregations, “parachurch” agencies, traveling personalities, media, music and more. Some folks accurately labeled “evangelical” have other primary identities. And don’t forget the minority evangelical factions within pluralistic “mainline” Protestant denominations.

Look at things this way: Groups in councils of churches and the like have shared organizations without shared belief. Evangelicalism has shared belief without a shared organization. In defining such a loose phenomenon, journalists will be reminded of Justice Potter Stewart’s remark on pornography. “I know it when I see it.”

Two of the book’s editors provided standard definitions, In an introduction to a 1984 book, Marsden said “we may properly speak of evangelicalism as a single phenomenon” with “conceptual unity” around five points: “the final authority” of the Bible, the “real, historical” character of God’s work recorded in the Bible, “eternal salvation only through personal trust in Christ,” “the importance of evangelism and missions,” and “the importance of a spiritually transformed life.”

That last point, often mis-characterized, does not require a dramatic moment of “born again” conversion or commitment. People in biblically conservative churches are often “transformed” gradually, but thoroughly.

Bebbington’s 1989 history of British evangelicalism defined the “special marks” as “conversionism, the belief that lives need to be changed; activism, the expression of the gospel in effort; biblicism, a particular regard for the Bible, and what may be called crucicentrism, a stress on the sacrifice of Christ on the cross.”

Confusingly, both the Marsden and Bebbington criteria depict not some distinctive evangelical ideology but ardor for pretty much what all of Protestantism stood for till recent times.

The Religion Guy advises writers to refine those definitions by adding traditionalism in doctrine and morals. Thus evangelicalism embraces the ancient belief in God as the Trinity (excluding “Oneness” Pentecostals, Latter-day Saints and Jehovah’s Witnesses despite some evangelical-like traits), and on morality opposes such innovations as openly gay clergy and same-sex marriages in church.

Note that movement-wide definitions omit certain sectors’ enthusiasm for end-times scenarios or attacks on evolution. Also they involve religious substance, not politics or folkways — but does that remain true in the Trump Era? Ask your sources.

Media treatments of U.S. evangelicals usually cover “white evangelicals,” often without saying so. Importantly, Banks notes a survey by the NAE and Southern Baptists showing 44 percent of African-Americans and 30 percent of U.S. Hispanics are evangelicals by religion (though distinct in socio-political terms).

Finally, as Noll and other contributors to the book observe, whatever the term signifies in the United States these days, evangelicalism remains the valid label for a worldwide, non-partisan, and thriving movement. The Lausanne Covenant from a 1974 international congress — part of the wider Billy Graham world — provides journalists a representative definition for this global aspect.

Media contact at Eerdmans is Laura Hubers, lbhubers@eerdmans.com or 616 - 234-0550.