Soviet espionage existed in the United States since the U.S.S.R.’s founding and continued until its dissolution in the 1990s. It reached its height in World War 2 and the early Cold War, especially to steam atomic weapon’s technology (revealed to the public with the trials and executions of Julius and Ethel Rosenberg, two Americans who fed intelligence back to the Soviets). The funnel for Americans into Soviet espionage was the Communist Party USA (CPUSA), a movement that attracted egalitarian idealists and bred authoritarian zealots. Throughout its history, the American Communist Party attracted a variety of seemingly contradictory people. Democratic, reform-minded individuals who wanted to end inequality worked alongside authoritarians and ideologues who espoused Soviet propaganda. These factions reached loggerheads following Nikita Khrushchev’s revelation of Joseph Stalin’s crimes, leading to the organization’s decline into political irrelevance.    To look at this history is today’s guest, Maurice Isserman, author of “Reds: The Tragedy of American Communism.”