At one point during the script development, after developing a case of what writer and director Emilio Estevez called "paralyzing writer's block," Estevez set the script aside. Later, he checked into a remote hotel on the Central California Coast, near Pismo Beach, to work on the script. When he checked in, the woman at the desk recognized him, and asked what he was doing there. "I'm writing a script about the night Bobby Kennedy was killed," he told her. Tears instantly welled in her eyes. "I was there," she replied. Estevez interviewed the woman, who had been a volunteer for Robert F. Kennedy in 1968. He turned her personal story, which included marrying a young man to keep him out of Vietnam, into the Diane Howser character. Estevez said, "She really helped me crack the spine of the story and give it a beating heart. After that, it just started to flow."
In many ways, writer and director Emilio Estevez felt that he was fated to make this movie all of his life. Just six years old when Robert F. Kennedy died, Estevez vividly remembers that night through a child's eyes, and seeing the horrific announcement that the Senator had been shot on television, and rushing to awaken his father, Martin Sheen, a long-time Kennedy supporter, with the shocking news. Soon after that, Sheen took his son to visit the spot where Robert F. Kennedy had delivered his final speech at the Ambassador Hotel, a heartfelt, impromptu call for American unity and action in the face of escalating rifts and violence. Estevez recalled: "I remember my dad holding my hand as we wandered through those grand halls, and I remembered my father talking about what we had lost."
The scene of Miriam Ebbers cutting her husband's hair was not in the script. Sharon Stone was supposed to pantomime cutting the hair, but she actually snipped his hair. William H. Macy's visibly tense reaction was real.
A few scenes were filmed at the Ambassador Hotel in Los Angeles, California, the real-life location of the Robert F. Kennedy assassination, during its demolition. The wing of the hotel they were using hadn't been touched by the demolition crew yet, in order to preserve items from the pantry where Kennedy was shot.
In a show of loyalty for this movie, all of the actors and actresses agreed to work for scale.