"Halstead and Lind drew explicitly on “The Radical Center: Middle Americans and the Politics of Alienation,” a sociological study published in 1976. Its author, Donald I. Warren, had supervised nearly 2,000 interviews with a cross-section of citizens, almost all of them white, in an effort to isolate the attitudes of “middle American radicals,” whose anger at political and social institutions had erupted in the early and mid-1970s. … Put roughly, “radicals” were blue-collar Catholics, and “average middles” were white-collar Protestants. The novelty of Halstead and Lind’s book lay in its suggestion that subsequent changes in demographics and party affiliation had collapsed the two warring factions into one. Between 1970 and 2000, the percentage of college graduates in the population at large had more than doubled, from one in 10 to one in four. Evangelicals had joined Catholics among the ranks of social conservatives. The working-class “flight” from the Democratic Party was all but completed in the 1980s and ’90s even as moderate Republicans began to vote for Democrats. The question Halstead and Lind tried to answer, whether this fusion of the two “middles” might form a new consensus, is again the most pressing issue of the day, with conflicting answers supplied by left and right, and with the outcome fluctuating from moment to moment, possibly confirming the authors’ guess that “the future of American politics may well belong to the major party that is first to renounce its more extreme positions.” This is why “The Radical Center” remains valuable even as the political realities that seemed to discredit its argument a decade ago have themselves proved fleeting."