Robert P. Jones, CEO of the Public Religion Research Institute, spells out the profound political and cultural consequences of a new reality--that America is no longer a majority white Christian nation. "Quite possibly the most illuminating text for this election year" (The New York Times Book Review).

For most of our nation's history, White Christian America (WCA) set the tone for our national policy and shaped American ideals. But especially since the 1990s, WCA has steadily lost influence, following declines within both its mainline and evangelical branches. Today, America is no...