By Alanna Durkin Richer

BOSTON (AP) --

He was once called the most likely American in the 20th century to become president. But Robert F. Kennedy's bid to follow in his older brother's footsteps as commander in chief was cut short the same way John F. Kennedy's White House term was: by a man with a gun.

Fifty years later, Bobby Kennedy's life and transformation into a liberal hero is coming to Netflix in a new four-part documentary series available Friday. Through archival footage and interviews with friends and staffers, "Bobby Kennedy for President" takes an in-depth look at what drove him to seek public office, the events that shaped him and his legacy decades after his assassination.

"If we want to understand why Bobby Kennedy was so important to people, we have to understand all of it," said Dawn Porter, director and executive producer, also known for "Gideon's Army" and "Trapped."

The series opens with a broadcaster's prediction that "no American in this century has ever been so likely to be president as Robert Francis Kennedy." It takes viewers through Kennedy's combative time as attorney general, and his depression after his brother's death, entry into the 1968 presidential race and assassination 83 days later.

The documentary explores Kennedy's growth on issues like civil rights, through the guidance of black leaders like John Lewis, now a Democratic congressman. In documenting Kennedy's journey from a "cop-at-heart" lawyer to polished politician, it highlights experiences that affected him, like a trip to the Mississippi Delta that opened his eyes to rural hunger.

Viewers hear from key figures in Kennedy's life, including Paul Schrade, who was shot in the head when 24-year-old Sirhan Sirhan fired at Kennedy on June 5, 1968. The series, produced by RadicalMedia, Trilogy Films and LooksFilm, also features interviews from Sirhan's brother, Munir Sirhan, and Juan Romero, the Ambassador Hotel busboy who was at Kennedy's side as he uttered his last words: "Is everybody OK?"

For Romero, a Mexican immigrant, it was one of the few times he has openly spoken about Kennedy's death — something he had felt guilty about for years since Kennedy stopped to shake his hand before the gunshots. Romero had met Kennedy the day before while delivering room service. Kennedy thanked him and shook his hand then, too.

"I never felt so American," Romero told The Associated Press.

Filmmakers spent more than a year gathering footage from museums, news outlets and presidential archives that transports viewers to a different time. Some of the footage, which shows Kennedy from his college days to the last day of his life, had never before been digitized and was at risk of being lost forever, filmmakers say.

"I didn't want this to be talking heads with pictures as the background," Porter said. "We wanted the archive to play out, to not be window dressing, but to let people watch that and absorb it and hopefully be in the moment, be taken back to that time," she said.

At a time when distrust of politicians is high, Porter said she hopes the series reminds viewers that people serving in public office can be human and flawed, but also inspirational.

"Without saying (Kennedy) was the perfect person, there's something comforting and inspiring to me about his willingness to try, his willingness to learn, his willingness to not give up," Porter said. "Right now we all need a little dose of not giving up."

Associated Press reporter Russell Contreras in Albuquerque, New Mexico, contributed to this report.

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