During a segment on HBO’s “Real Time with Bill Maher” in August, activist Christopher Rufo astonished the studio audience when he said the Watergate scandal that toppled President Richard Nixon “was a setup from start to finish.” Maher muttered, “Oh, geez,” to which Rufo replied with a grin and a prediction: “Nixon vindication by 2035.” The Watergate scandal has long been viewed as a defining moment in presidential corruption and accountability, prompting a series of government transparency reforms and influencing generations of journalists. It became a shorthand comparison for political scandal and lent the omnipresent “-gate” suffix to many that...