BEVERLY HILLS, Calif. – In the thick of the presidential campaign, a documentary about a political wife wouldn’t seem to offer respite from the clatter.

But that’s exactly what “Ethel,” an intimate, affectionate look at Ethel Kennedy by her youngest child, manages to do. It’s a heartfelt reminder of public service’s rewards and heaviest demands, elements that can be lost in the moment’s rough-and-tumble.

It also honors a rarely interviewed Kennedy wife who was eclipsed by her more glamorous sister-in-law and sister in tragedy, Jacqueline Bouvier Kennedy.

Debuting tonight on HBO at 9, “Ethel” offers the life and times of Robert F. Kennedy’s widow through the lens of accomplished filmmaker Rory Kennedy, born six months after her father’s 1968 assassination.

Her mother is a reluctant star but, with the help of siblings and a rich film and photo collection, Rory Kennedy creates a portrait of a feisty, devout and socially concerned woman who carried – and carries – on despite the shattering loss.

“Ethel” weaves family memories with the major events of her husband’s political life, including the Cuban missile crisis that confronted his brother, President John F. Kennedy, and RFK as U.S. attorney general.

It also creates a charming portrait of Ethel Skakel as a girl who would rather handicap the ponies than study her schoolbooks and who raised her children to be game competitors, never whiners, and never shrinking violets.

But Ethel Kennedy’s on-camera discomfort marks her as clearly out of step with the Facebook crowd. So why agree to the project?

“Because it was Rory who asked,” replied Kennedy, 84, in an interview in which she kept her answers short, pointed and invariably self-effacing.

Asked to assess the film, she replied: “How remarkable (Rory) is that she can pull something out of nothing. It’s not like I’ve ever done anything. It’s like I was just there.”

Rory Kennedy quickly jumped in.

“It’s consistent with how my mother speaks about herself. She has accomplished so much in her life and done extraordinary things,” she said. “But as you can see, she’s not comfortable giving herself credit for it.”

The film paints Ethel Kennedy as an exemplary spouse, one who helped her husband overcome the self-doubt that came with being the smallest of his large, competitive family.

Ethel Kennedy’s determination remains unflagging. While reluctant to discuss herself, she launches energetically into detailing efforts by the Robert F. Kennedy Center for Justice and Human Rights to improve conditions for New York farm workers.

During a Q&A with reporters, Ethel Kennedy credited her Catholic faith with helping her “get through everything,” including the loss of her husband five years after President Kennedy was assassinated.

“When we lost Bobby, I would wake up in the morning and think, he’s OK. He’s in heaven, and he’s with Jack, and a lot of my brothers and sisters, and my parents,” she said.