“Reaganland” is the new volume in Rick Perlstein’s long chronicle of the American conservative movement; the four books, which he began publishing in 2001, run some 3,000 pages in total. While the author is left of center politically, the series has been praised by William F. Buckley, Jr., and George Will, among others. Andrew Marantz finds that Perlstein uniquely captures the mood of the country and how intangible, emotional factors in the electorate influence political shifts. Perlstein tells Marantz that Trump is neither an aberration from traditional conservative politics nor a continuation but a throwback to an earlier, unruly time in the Republican Party, when its ideologically more disparate umbrella contained open racists, anti-Semities, and conspiracy theorists not so unlike QAnon. The Party became ever more disciplined as the Goldwater era moved into what Perlstein calls Reaganland. “Disciplining what got said, behind closed doors and in public,” he says, “was an enormous part of the political work of [Reagan’s] Administration.”