The movement also faces a donation crisis as older evangelicals, who give a disproportionately large share, age. Unless younger evangelicals radically increase their giving, the movement will be further strained.

Evangelicals have not adapted well to rapid shifts in the culture — including, notably, the move toward support for same-sex marriage. The result is that evangelicals are increasingly typecast as angry and repressed bigots. In 2007, the Institute for Jewish and Community Research, in a survey of 1,300 college professors, found that 3 percent held “unfavorable feelings” toward Jews, 22 percent toward Muslims and 53 percent toward evangelical Christians.

To be sure, college professors are not representative of the population, and, despite national trends of decline, evangelicals have many exceptional ministries. Most metropolitan areas in the United States have at least one thriving megachurch. In New York City, Redeemer Presbyterian and the Brooklyn Tabernacle pack multiple services every weekend. A handful of other churches, like North Point Community Church in Alpharetta, Ga., and Saddleback Church in Lake Forest, Calif., see more than 20,000 worshipers each weekend. Savvy ministers like the Rev. Craig Groeschel, founder of LifeChurch.tv, are using new technologies to deliver the “good news.”

The pulse of evangelicalism is also shifting, in many ways for the good, from American politics to aid for the global poor, as evidenced in books by the Rev. David Platt, the Rev. Max Lucado and the Rev. Timothy Keller. Evangelicals are still a sophisticated lot, with billions in assets, millions of adherents and a constellation of congregations, radio stations, universities and international aid groups. But all this machinery distracts from the historical vital signs of evangelicalism: to make converts and point to Jesus Christ. By those measures this former juggernaut is coasting, at best, if not stalled or in reverse.

How can evangelicalism right itself? I don’t believe it can — at least, not back to the politically muscular force it was as recently as 2004, when white evangelicals gave President George W. Bush his narrow re-election. Evangelicals can, however, use the economic, social and spiritual crises facing America to refashion themselves into a more sensitive, spiritual and humble movement.

We evangelicals must accept that our beliefs are now in conflict with the mainstream culture. We cannot change ancient doctrines to adapt to the currents of the day. But we can, and must, adapt the way we hold our beliefs — with grace and humility instead of superior hostility. The core evangelical belief is that love and forgiveness are freely available to all who trust in Jesus Christ. This is the “good news” from which the evangelical name originates (“euangelion” is a Greek word meaning “glad tidings” or “good news”). Instead of offering hope, many evangelicals have claimed the role of moral gatekeeper, judge and jury. If we continue in that posture, we will continue to invite opposition and obscure the “good news” we are called to proclaim.

I believe the cultural backlash against evangelical Christianity has less to do with our views — many observant Muslims and Jews, for example, also view homosexual sex as wrong, while Catholics have been at the vanguard of the movement to protect the lives of the unborn — and more to do with our posture. The Scripture calls us “aliens and exiles” (1 Peter 2:11), but American evangelicals have not acted with the humility and homesickness of aliens. The proper response to our sexualized and hedonistic culture is not to chastise, but to “conduct yourselves honorably among the Gentiles, so that, though they malign you as evildoers, they may see your good deeds and glorify God” (1 Peter 2:12).