The Claremont Institute, a right-wing think tank in California, has in recent years become increasingly influential in Republican circles. In 2016, its goal was to turn Donald J. Trump into a legitimate candidate — and then it did . The journalist Elisabeth Zerofsky traces the origins of the divisive organization, explaining how it made the intellectual case for Trumpism but also how, with ties to Ron DeSantis and John Eastman, the think tank has become a home for “counterrevolutionary” politics that go far beyond the former president.