Caitlyn Jenner, center, stands trackside to watch the seventh race as the Del Mar Thoroughbred Club opened its annual summer meet in Del Mar, California. Photo: Benoit Photo via AP

Caitlyn Jenner, center, stands trackside to watch the seventh race as the Del Mar Thoroughbred Club opened its annual summer meet in Del Mar, California. Photo: Benoit Photo via AP

NEW YORK (AP) — It’s the next step in the biggest celebrity story of the year.

It’s the long-awaited debut of Caitlyn Jenner’s docuseries charting her new life as a transgender woman.

Fittingly, “I Am Cait” (premiering Sunday at 8 p.m. EDT on E!) opens with the former Bruce Jenner, her ample tresses in huge rollers, at home getting hair-and-makeup treatment as she beholds a giant blowup of her bombshell Vanity Fair cover that followed her April interview with Diane Sawyer.

Yes, Jenner’s transition from Bruce to Caitlyn has been a highly orchestrated spectacle, with “I Am Cait” the latest phase of the campaign. And, typical of celeb-reality shows, there isn’t a scene in this first of eight episodes that doesn’t seem stage-managed to push the starry uber-narrative along.

Even so, there is something more substantial going on here. A gratifying measure of authenticity manages to bypass the celebrity trappings.

Jenner’s mother and two sisters help. Delivered to Jenner’s seaside California compound for their first encounter with her as a woman, they seem refreshingly like regular folks who are genuinely focused on a family member they love and support, never mind all the lights and cameras there to capture every moment.

“It’s going to be so difficult for me to think of you as ‘she,’ and say ‘Caitlyn’ when I want to speak with you,” her mother says. “It’s going to take some getting used to, but I want to do what you want.”

At the other end of the authenticity scale are stepdaughter Kim Kardashian and her husband, Kanye West. They are seen in a cameo appearance that plays as unintended comic relief, with Kardashian never doffing her floor-length coat (she blames her modesty on her pregnancy, yet it smacks more of, “I don’t show my body except for my own projects”) and with West explaining that his shoelaces are untied because they’re unnecessary since his shoes are really slippers (“the laces are sort of after the fact”).

Kardashian takes the time to survey Jenner’s closet full of new women’s fashions. Then she and West make their hasty exit.

Such interludes undercut the dignity of Jenner’s challenges, and make what she is going through arguably less relatable to an audience that needs to relate.

On the other hand, fame claims attention, and the celebrity machine for Caitlyn Jenner, including “I Am Cait,” has been impossible to miss. With “Cait,” she will have a weekly pulpit and a guaranteed flock to whom she knows how to deliver her message loud and clear.

“The tremendous amount of support that I’ve gotten has been overwhelming, but you also have to realize that it’s not this way for everybody,” she takes pains to point out.

More than once, she cites the lack of support from family, friends and outsiders experienced by far too many in the trans community, as well as the high murder rate and many suicides.

Jenner says she relates: “I’ve had some very dark moments in my life. I have been in my house with a gun and said, ‘Let’s just end it right here.'”