Worst of all, the court order for surveillance of Mr. Page was renewed three successive times at the behest of officials including Mr. Comey, the FBI’s then Deputy Director Andrew McCabe, and Deputy Attorney General Rod Rosenstein. To anyone who has studied how Hoover’s FBI worked, this continuing approval immediately calls to mind the bureau’s never-ending surveillance of King’s closest adviser, Stanley Levison. Year after year, the wiretaps of Levison produced no evidence to support the FBI’s hypothesis that he was a Soviet agent. Still, successive attorneys general, including Bobby Kennedy, readily approved the FBI’s surveillance of Levison and his family.

At first blush, Mr. Rosenstein might welcome the comparison to RFK. But the important point is that the modern Justice Department’s surveillance of law-abiding American citizens—whether in New York or Dallas—is no more defensible than the 1960s blanket coverage of Levison and King.

Yet that bright truth is, at the moment, being outshone by Democratic lawmakers’ eagerness to cover up, excuse and defend FBI behavior that their predecessors of the 1970s would have readily denounced. The ignominious irony is that judgment-blurring partisan hatred is leading many Democrats to ignore and forsake the lessons that the FBI’s history so richly teaches.