Molly Worthen is an assistant professor of history at the University of North Carolina at Chapel Hill.

In 1968, Mark Hatfield, one of America’s most prominent evangelical politicians, wanted to abolish the draft and clandestinely wore a Eugene McCarthy pin under his lapel. A Republican senator from Oregon, Hatfield had fans in evangelical churches around the country. When organizers of the 1973 National Prayer Breakfast invited him to address Richard Nixon, Henry Kissinger and other conservative luminaries (the Vietnam War was a “national sin and disgrace,” he told them), he based his remarks on a text written by a renegade seminarian named Jim Wallis — a former member of Students for a Democratic Society who believed that being “pro-life” meant hating war and poverty as much as abortion.

If the historian David R. Swartz is right, Hatfield, Wallis and their supporters were not just forgettable anomalies in the inexorable rise of the Christian right. The early 1970s were not “the ­Reagan ­Revolution-in-waiting,” he contends, but an unsettled era when evangelicals’ ambivalent political impulses had not yet hardened and left-leaning activists had prospects nearly as bright as their peers on the right. Today, in the midst of Capitol Hill gridlock and the slugging matches of partisan super PACs, “Moral Minority” jogs our historical memory and challenges our imagination: not so long ago, the American political landscape was very different.

Swartz tells his story through profiles of activists, politicians and evangelists who tried to convince fellow believers that the Gospel demands social justice. His subjects range from progressive academics like the Baptist civil rights activist and philosopher John Alexander, who roused student consciousness through his fiery teaching at Wheaton College in Illinois, to Wallis’s grungy Christian commune in Washington and the Christian World Liberation Front in Berkeley. Other people pushed evangelicals beyond their Anglo-American male comfort zone: black evangelists electrified the evangelical conference circuit; evangelical feminists decried patriarchy; Latin American preachers held Americans accountable to the needs of poor Christians in the global South. “Moral Minority” is a vivid topography of a little-understood corner of evangelical thought. It is not an account of a political movement — because there was no movement to speak of. This is a story of failures and might-have-beens, but it is just as illuminating as a history of political success....