The liberal Protestant denominations, long the most influential of America's mainline religious bodies, have suffered serious membership losses since the late 1960s. The principal sources of the losses are in the failure of the children of members to remain affiliated; this failure has been traced to a value shift that began among college-educated youth in the 1960s. Although this shift caught the liberal churches by surprise, their leaders contributed to the intellectual climate that made it possible. This climate was created in the 1930s by Reinhold Niebuhr in his critique of the optimistic religious liberalism of his day as the self-serving ideology of the bourgeoisie. As an alternative he urged theology to recover a sense of the sinful and tragic side of life and urged Christians to support the struggles of oppressed peoples. Although these themes profoundly affected liberal Protestant leaders, they failed to attract most lay people. In the 1950s Protestant intellectuals began mounting a frontal assault on the popular piety of the laity. This assault, which eventually extended even to theistic belief itself, was thematically similar to secular intellectuals' critiques of American culture and institutions, which were later embodied in an exaggerated form in the youth rebellions of the 1960s. If the liberal churches are to recover their strength and cultural influence they will have to make liberal Christianity more relevant and compelling to its own constituency.
