Backstage in the arena, a little girl in Mary Janes pushes her brother in a baby carriage, stopping a few yards shy of a heavy, 100-foot-long black curtain. The curtain splits the arena in two, shielding the children from an audience of 4,000 people clapping their hands in time to “The Battle Hymn of the Republic.” The music accompanies a video “Salute to Military Heroes” that plays above the stage where, in a few moments, the children’s mother will appear.

When the girl, Piper Palin, turns around, she sees her parents thronged by admirers, and the crowd rolling toward her and the baby, her brother Trig, born with Down syndrome in 2008. Sarah Palin and her husband, Todd, bend down and give a moment to the children; a woman, perhaps a nanny, whisks the boy away; and Todd hands Sarah her speech and walks her to the stage. He pokes the air with one finger. She mimes the gesture, whips around, strides on four-inch heels to stage center, and turns it on.

A prosiac lead, but accurate? Maybe not.

As first reported by Politico on Thursday, the baby in the carriage is not Trig; it's the young son of St. Louis conservative activist Gina Loudon, whose child, Samuel, also has Down syndrome.

Loudon, a former candidate for State Senate who's become increasingly involved in Tea Party politics, did advance work for Palin in the 2008 campaign. The two developed a personal bond because both their children were born with Down syndrome.

After the piece appeared in the current edition of Vanity Fair, Loudon said she was sent the piece by supporters who knew it was Samuel, and not Trig, at the May event near Kansas City.

"The minute they read it they said, 'Trig wasn't there that day,'" Loudon said in an interview this morning.

 Loudon said she saw the Vanity Fair writer backstage, and attempted to clear up any misunderstanding.

"When I grabbed Samuel and walked past the stage, he said, 'Oh, are you the nanny?" Loudon recalled. "And I said, 'No, I'm not the nanny I'm the mother.'"

Loudon said she was "so caught off guard by the question is the only reason I remember it."

Gina and her husand John, a former State Senator, adopted Samuel about five years ago as a newborn. She says it's not uncommon for people to confuse Samuel with Trig -- they actually do look alike.

"Samuel looks very much like Trig -- so I always have to explain this to the press," Loudon said.

Loudon said she attempted to explain to the Vanity Fari writer that the baby in the carriage as not Trig, but it evidently did not stick

"I told him that. And he ignored it," Loudon said. "It's not even like he didn't fact check -- he just ignored facts."