Barry Goldwater, the Republican senator from Arizona who ran for president in 1964, made his priorities clear: "My aim," he famously said, "is not to pass laws, but to repeal them." Goldwater's comment was seized upon by the historian Richard Hofstadter in his 1965 book, The Paranoid Style in American Politics. Although claiming to be conservative, the senator, Hofstadter maintained, was anything but. "How are we to explain," he wanted to know, "the character of a 'conservative' whose whole political life has been spent urging a sharp break with the past ... ?" It seemed remarkable that a country as modern, wealthy, and stable as the United States was witnessing such deep, persistent, and intransigent right-wing discontent. By using the term "paranoid," Hofstadter sought an answer in the inner workings of the mind, as if what Goldwater represented could best be explained not by analyzing polling data, but by psychoanalyzing officeholders.

These days, repealing laws rather than passing them is the single most prominent feature of the way some conservative Republicans in Congress have approached their job. Does a term such as "paranoid" therefore apply to Ted Cruz, Mike Lee, and Rand Paul, in the Senate, and to Tea Party members in the House of Representatives, all of whom have done their best to defund Obamacare, indeed to act as if President Obama had no mandate to govern?

In many ways, the answer must be no. Although often described, especially by Senate Majority leader Harry Reid, as insane, hard-right Republicans can be viewed as hyperrational: They have forced the country to debate issues such as the deficit and taxes on their terms. In other ways, Hofstadter's term "paranoid" fails to convey the extent to which psychology, rather than politics, helps explain the actions of today's politicians who adhere to the radical right....