Powers was riding in the presidential motorcade when JFK was assassinated in Dallas in 1963. He accompanied the president's body back to Washington, and helped care for the Kennedy children in the weeks following the assassination.
Described by historian and former Kennedy aide Arthur Schlesinger Jr. as a man of "exceptional sweetness and fidelity," Powers soon was known as Kennedy's "Sancho Panza."
"Dave Powers was a loyal and devoted friend whom my mother and father adored," said JFK's daughter, Caroline Kennedy, president of the Kennedy Library Foundation. "I will always be grateful for his personal kindness and for his tireless efforts on behalf of the Kennedy Library."
The man who called himself "just a newsboy who met a president" had been sought out by the wealthy Kennedys in the early days of JFK's political career because he was closely connected to Boston's blue-collar Irish-American families.
The child of Irish immigrants, Powers was reared in the Charlestown section of Boston. When he was a boy, he hawked newspapers on the waterfront, spent Sundays at a local church assisting at five Masses, and knew almost everyone in the neighborhood.
So it was no surprise that a campaign worker directed Kennedy to Powers' door when the future president was campaigning for Massachusetts' 11th Congressional District seat in 1946.
Powers had been supporting the rival candidate, but he was so taken by the young Kennedy that he changed camps, and remained a personal and family aide for the rest of his life.
Powers initiated JFK into the rough and tumble of Boston campaigning and in how to deal with the ordinary folk of the city. At one rally, he convinced Kennedy to improve the impact of a high-toned speech by emphasizing that his parents were natives of the district.
In later years, Powers traveled thousands of miles with Kennedy on various campaigns and missions.
After Kennedy was elected president in 1960, the man who called himself a "three-decker Irishman," referring to the houses of Boston's Charlestown and other Irish-American enclaves, became a special assistant in the White House.
Powers served as an unofficial greeter at White House functions and as a full-time friend who often had private chats with the president during Kennedy's time in office.
President Kennedy, he said, "was the greatest man I ever met and the best friend I ever had."
Powers was known for his humor and his indifference toward those with lofty titles whom he welcomed to the White House. He once told the visiting Shah of Iran, "I want you to know you're my kind of Shah."
Friends aid Powers remembered Kennedy's campaigns so well - congressional, senatorial, and presidential - he could rattle off the exact number of votes the president got in each of his elections.
After JFK's assassination, Powers went on to help in former Sen. Robert F. Kennedy's campaigns. He also began work assembling records and memorabilia for the JFK Library in 1964. He served as its museum curator from its opening in 1979 until he retired in 1994.
In 1975, JFK's legacy came under serious fire when Judith Campbell Exner claimed that she had been both Kennedy's White House mistress and the girlfriend of a Chicago mobster and that Powers had arranged meetings between her and the president.
On one occasion when she had a fight with Kennedy, Exner said Powers tried to calm her down by escorting her on an informal stroll through the White House.
Powers denied knowing Exner and once said "the only Campbell I know is chunky vegetable soup."
Powers, who served in the 14th Air Force in China, Burma and India during World War II, had worked in publishing and then as director of the Boston Housing Authority's recreation department in South Boston. He later became a member of the State Housing Board.
He is survived by his wife, Jo, a son, David John; daughters Diane and Mary Jo, and three grandchildren.
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