Mr. Radosh is a columnist for PJ Media and an adjunct fellow at the Hudson Institute. He is the co-author of "Spain Betrayed: The Soviet Union in the Spanish Civil War" (Yale University Press, 2001).

For many years, the American left has combed the past for history lessons that will aid their effort to move the United States toward European-style social democracy, if not a full-fledged socialist utopia. The most successful leftist intellectual in that enterprise was the late Howard Zinn, whose books—such as "A People's History of the United States," first published in 1980—have sold millions of copies and are still used by high schools and colleges nationwide. Zinn believed that by emphasizing the struggles of working people, women and people of color against their supposed oppressors, his work could mobilize a new generation to carry on the fight of yesterday's radical heroes.

That search for a usable past has been taken up in a new form by filmmaker Oliver Stone and historian Peter Kuznick in both their Showtime television series, "Oliver Stone's Untold History of the United States," and in the accompanying book of the same name. Mr. Kuznick, who wrote the volume and whose outlook frames the series, is frank about his mission.

He once wrote in a book of essays that he sees his role as a professor to be that of "creating a bridge between leftist and more moderate students," so that he can "try to radicalize some of the more moderate and liberal students" who accept our political system instead of working for real radical change. Those who support "liberal capitalism," he wrote, are "blind to the lessons of history."...