Joseph E. Persico, a best-selling historian and biographer who wrote about espionage during World War II and the leadership and romantic inclinations of Franklin D. Roosevelt, and who was co-author of Colin Powell’s autobiography, died Aug. 30 at a hospital in Albany, N.Y. He was 84.

He had a heart ailment, said his wife, Sylvia LaVista Persico.

Mr. Persico worked with the U.S. Information Agency early in his career and later served as chief speechwriter for New York governor and then vice president Nelson A. Rockefeller before becoming an independent historian.

Among his dozen books, Mr. Persico published three popular and well-received studies of Roosevelt, examining his various roles as presidential leader, military commander and keeper of secrets, both official and private.

In his 2008 book, “Franklin & Lucy,” Mr. Persico offered persuasive evidence that the president carried on a decades-long affair with Lucy Mercer Rutherfurd, a onetime secretary to Eleanor Roosevelt.

The romance continued through Roosevelt’s presidency, Mr. Persico believed. Rutherfurd visited the White House more than 40 times under an assumed name, often met Roosevelt in out-of-the-way locations and was with him when he died in 1945.

“If the relationship was simply the shared companionship of old friends,” Mr. Persico wrote, “why all the machinations to conceal it?”

In his best-selling 2001 book, “Roosevelt’s Secret War: FDR and World War II Espionage,” Mr. Persico described Roosevelt’s cagey but effective ways of consolidating the power of the presidency: “FDR compartmentalized information, misled associates, manipulated people, conducted intrigues, used private lines of communication, scattered responsibility, duplicated assignments, provoked rivalries, held the cards while showing few, and left few fingerprints.”

Mr. Persico was a member of Rockefeller’s inner circle for 11 years, including his tenure as Gerald R. Ford’s vice president in the 1970s. In 1982, Mr. Persico published “The Imperial Rockefeller,” about his onetime boss, and also wrote authoritative biographies of broadcast journalist Edward R. Murrow and CIA director William J. Casey.

His 1990 book about Casey touched on espionage during World War II, which was one of Mr. Persico’s favorite subjects. Long before he became CIA director in the 1980s, Casey worked for the Office of Strategic Services, the wartime spy agency that was a precursor to the CIA.

In reviewing the biography for the New York Times, historian Michael Beschloss praised Mr. Persico for weaving the elusive strands of Casey’s life into “a lively and balanced narrative that conveys [Casey’s] complex mixture of earthy selfishness and higher loyalties.”

Several of Mr. Persico’s books became bestsellers, but none was as successful as “My American Journey,” his 1995 collaboration with Powell, the retired Army general who served as chairman of the Joint Chiefs of Staff and later as secretary of state under George W. Bush. The two met in Powell’s home in McLean, Va., over a period of 20 months.

“We clicked early, both of us compulsive workers,” Mr. Persico told the Times in 1995. “My American Journey” became a No. 1 bestseller, but Mr. Persico said he sometimes had to drag Powell’s personal story out of him.

“He did two Vietnam tours, and he gave me bare bones,” Mr. Persico recalled. “And I said, ‘Wait a minute. That’s it?’ You served in the Army during this country’s most controversial war and its most sundered period since the Civil War. You saw friends die. You can’t let it go like this.’ ”

Joseph Edward Persico was born July 19, 1930, in Gloversville, N.Y., where his parents worked as glove makers. He was a 1952 graduate of what is now the University at Albany.

He served as a Navy officer during the Korean War and worked in state government in New York before joining the USIA in the late 1950s. He was assigned to Rio de Janeiro, Buenos Aires and Washington, where he once shared an elevator ride in 1961 with Murrow, the renowned radio and television journalist who was USIA director at the time.

In his widely lauded 1988 biography of Murrow, Mr. Persico recalled the encounter.

“My eye went automatically to his hand, where indeed there was a cigarette,” he wrote. “I remember thinking that Ed Murrow looked the way Ed Murrow was supposed to look. . . . I remember too an electrical field around the man that the others in the elevator pretended not to feel, the stiff silence merely heightening the voltage.”

Mr. Persico’s other books included the “Eleventh Month, Eleventh Day, Eleventh Hour” (2004), about events surrounding the World War I armistice; “Roosevelt’s Centurions: FDR and the Commanders He Led to Victory in World War II” (2013); and “Nuremberg: Infamy on Trial” (1994), a fast-paced account of the postwar trials of Nazi officials. The book formed the basis of a two-part television movie in 2000 starring Alec Baldwin, Christopher Plummer and Max von Sydow.

Mr. Persico’s survivors include his wife of 55 years, Sylvia LaVista Persico of Guilderland, N.Y.; two daughters, Vanya Perez of Charleston, S.C., and Andrea Holder of Denver, Pa.; a brother; a sister; and five grandchildren.

In conducting research for his books, Mr. Persico said he borrowed his interviewing technique from Murrow, who often maintained a stoic silence that his subjects were eager to fill.

“When he spoke with politicians or celebrities,” Mr. Persico said in 1989, “he listened to their first answer to his question and then stared at them expectantly, waiting for them to go deeper. Inevitably, they did. He would throw away the first response and use the much more interesting material in the unrehearsed version.”