From Smithsonian.com by David Mislin:
May of 1968, a high-profile trial began in Boston that dramatically illustrated a larger phenomenon fueling the rise of conservative Christianity in the United States.
Five men had been charged with conspiracy for encouraging Americans to evade the draft. One of the prominent defendants in the trial was a Presbyterian minister and Yale University chaplain, William Sloane Coffin Jr..
Coffin, like many ministers, vehemently opposed the Vietnam War, but many ordinary churchgoers supported it. This disagreement divided denominations. Eventually, many alienated Protestants abandoned mainline churches in favor of the evangelical congregations that formed the core of the new conservative Christianity.
Coffin was a prominent figure in mainline Protestantism, the term given to denominations like Episcopalians, Methodists and Presbyterians. These were the churches of the middle- and upper-class establishment, and their leaders had long enjoyed close connections to political elites.