According to history professor Michael O'Brien, on the evening of February 7, 1960, the "stunningly beautiful" Ms. Campbell met Senator John F. Kennedy at Frank Sinatra’s table at the Sands lounge in Las Vegas. Kennedy appeared to be quite taken with Ms. Campbell. She later said in her autobiography that when she talked to him, “it was as if every nerve and muscle in his whole body was poised at attention. As I was to learn, Jack Kennedy was the world’s greatest listener.” The next day Kennedy invited her for lunch at Sinatra’s suite. Kennedy became enamored with her and called her almost daily. They had their first intimate encounter the following month on March 7, 1960 at the New York Plaza Hotel. In her autobiography she describes subsequent encounters including one in the Kennedy home (when Jacqueline was away) and another at Kennedy's suite in Los Angeles during the Democratic Convention.
The relationship lasted for about two years. In her 1977 memoir, she said that she frequently visited him in the White House after he was elected president. Her account was supported by phone records and other documentation.
A few months after she met Kennedy, Sinatra introduced Campbell to a man who was introduced to her as "Sam Flood," but who was actually Sam Giancana, a leading figure in the Chicago Mafia. She said that she also became intimately involved with him.
Throughout the fall of 1961 into the spring of 1962, she said that she continued seeing
Kennedy in the White House. She said that Kennedy’s secretary, Evelyn Lincoln, made reservations for her at the Mayflower Hotel. In the evening, a White House car drove her to the East Gate, used by tourists during the daytime. She would meet Kennedy either in the entrance hall or an aide would escort her to an elevator that led to the family quarters.
By late spring of 1962, their romance had cooled off. Kennedy called her less frequently. She said “It happened so gradually that I wasn’t really aware that it was over until long after it had ended."
Campbell received national media attention in 1975 when she testified before the Senate Church Committee on Government Operations and Intelligence. The committee was investigating CIA assassination attempts. Mobster Johnny Roselli, a Giancana associate, had testified to the committee about Mafia involvement in the CIA attempt on Fidel Castro's life. The committee report, released in December 1975, said that a "close friend" of Kennedy's, had also been a close friend of mobsters John Roselli and Sam Giancana." Campbell's identity as the close friend was leaked to the Washington Post, and her name was published both in the Post as well as in the New York Times also published it. The Committee subpoenaed Campbell. By then she was married to golfer Dan Exner, and was known as Judith Exner. She called a press conference and denied any knowledge of Mafia involvement with Kennedy.
In 1977, Exner published her memoir entitled Judith Exner: My Story. In the book she said that her relationship with Kennedy was entirely personal. She also said that Frank Sinatra later introduced her to Sam Giancana, with whom she also became intimate. She said that Giancana never asked her for any information related to Kennedy.
In the book Exner also alleged that Kennedy brought prostitutes to the White House swimming pool. She said that President Kennedy's Special Assistant, David Powers, helped set up encounters with President Kennedy. Powers denied this.
In a 1988 interview with Kitty Kelley of People magazine, Exner said that she had lied to the Church Committee and in her memoir out of fear of Mafia retaliation. She told Kelley that Kennedy had asked her to contact Giancana, and she helped set up a meeting between them during the 1960 presidential election. For about 18 months in 1960–1961, "Exner claimed she served as the president's link with the Mob. She crisscrossed the nation carrying envelopes between the president and Giancana, and arranged about 10 meetings between the two." She claimed these messages concerned plans to assassinate the Cuban president Fidel Castro.
In 1997, in separate interviews with Liz Smith of Vanity Fair and Seymour Hersh, Exner said that Kennedy told her of his plans related to Cuba, and used her to carry money to Giancana, as well as to arrange numerous meetings between the two. She also told Smith that she terminated a pregnancy which was the result of her last encounter in 1962 with Kennedy. She also said that she had delivered payoffs from California defense contractors to the Kennedys, including Robert F. Kennedy. These allegations are not supported by any corroborating witnesses or by any documents. Her earlier accounts of her affair with Kennedy were supported by FBI reports, Secret Service and White House phone logs and staff documentation, but nothing of this nature exists to support the allegations she made in 1997.
Judith Campbell Exner lived in Newport Beach, California until her death. She died on September 24, 1999 in Duarte, California from breast cancer. Her memoir was adapted as a made-for-TV movie in 2002, entitled Power and Beauty in which she was played by Natasha Henstridge.