Phyllis McGuire, one of the three McGuire Sisters, and Sam Giancana, a high-profile Mafia boss, were lovers. During the 1950s and 1960s, the McGuire Sisters were a famous female singing group in the United States. Phyllis McGuire and Sam Giancana's romance is the subject of an HBO movie, "Sugartime."
The McGuire Sisters' ended as a group in 1968. Phyllis' relationship with Giancana is thought to have been a contributing factor to the end of the group, though Phyllis continued to perform as a solo artist afterwards. Barbara Walters implied in an interview once that Phyllis' wealth came from her continuing relationship with Giancana, though this was refuted by Phyllis herself. Nevertheless, her association with Giancana and the Mafia continued to dog her throughout her life; rumors have reappeared occasionally about her intentions to write a tell-all memoir about Giancana, but have remained unfounded, as of 2015.
Giancana and the Kennedys may have had close ties going back to Joseph P. Kennedy, who may have met Giancana during the Prohibition, according to the National Geographic. Giancana was also associated with Frank Sinatra, a known friend of the Kennedys, and may have donated to John F. Kennedy's presidential campaign. Since JFK's death, rumors have spread that Giancana rigged elections on JFK's behalf. A shared mistress, Judith Campbell Exner, has stated she was asked to ferry correspondence between the two men.