In the 1950s, for example, the National Lawyers Guild, an association of progressive lawyers formed as an alternative to the segregated, anti–New Deal American Bar Association, was preparing a report detailing the FBI’s illegal wiretaps and dirty tricks. The FBI, after discovering the plan through its surveillance of the organization, drafted a report asserting that the National Lawyers Guild was an agent of Moscow. Only a tool of the Soviet Union, after all, would assert that the FBI engaged in illegal surveillance. The House Un-American Activities Committee published the report under its own name.

A couple decades later, the hubris of HUAC’s most famous alum — forever immortalized in his utterance “when the president does it that means it’s not illegal” — would send scholars scrambling for a new term to describe Nixon’s power grabs. Arthur Schlesinger Jr responded with the idea of the imperial presidency.

Two key components of Schlesinger’s concept were the president’s increasingly unilateral war-making — Nixon bombed Cambodia without congressional authorization — and the political uses of intelligence. The FBI is not merely a law enforcement agency; it is also an intelligence agency. Its domestic intelligence capabilities are the direct fruit of its role as a political police, and have been useful for thwarting domestic antiwar sentiment.

With his brazen actions, Nixon crossed an important threshold. He investigated his establishment opponents and illegally surveilled his counterparts in the Democratic Party. His crime was not subverting the democratic process — electoral subterfuge, suppression, and criminal prosecution of radical groups were and are a venerable American tradition — but instead harassing elected Democrats.

The Imperial Bureau