Sam was involved in the Kennedys blackmailing of Marilyn with provocative photos taken of her at the Cal-Neva Lodge, also taking a turn with the intoxicated Marilyn.

It is said that Giancana wanting revenge, came up with the plan to introduce Kennedy to Marilyn Monroe and then expose an affair between the two. Marilyn was bed hopping between the Kennedy brothers and confessed to Sam that she was in love with Bobby. Sam never exposed the affairs between Marilyn and the Kennedy brothers.

Concerning her death, it is said that JFK and Joe Kennedy are said to have arranged the hit, as her calls to the White House and Justice Department were causing trouble. She not only jeopardized the Kennedy dynasty but also national security, as Bobby had blabbed information about the Castro hit to Marilyn. They asked Giancana to take care of her and he agreed, wanting to be as close to the Kennedys as possible.

Giancana simply revised his plan from exposing an affair to killing Marilyn and then putting the blame on the Kennedys. However, he was angered when the newspapers did not even implicate the Kennedy brothers after Marilyn's death.