Every Democratic president since Lyndon Johnson -- Jimmy Carter, Bill Clinton and Barack Obama -- has raised the hope that he would bring with him a new era of progressive reform. The legislative torrents of the New Deal and the Great Society -- a few brief years in the 1930s and the '60s that fundamentally reshaped the nation's economy and society -- are the templates that fire the liberal imagination.

Two great liberal historians -- the Arthur Schlesingers, senior and junior -- posited a cyclical theory of American political history, in which periods of progressive advance alternate with times of conservative reaction once every generation. And even when liberals have discounted this theory as too mechanistic, their hearts, if not their heads, have responded to the election...