Maya Soetoro-Ng; Photo: Lucy Pemoni / AP

Barack Obama rolls out a new campaign weapon this week: his half-sister, Maya Soetoro-Ng, who hits the campaign trail on Thursday. The 37-year-old Soetoro-Ng, a high-school teacher in Honolulu whose red hatchback is plastered with her brother’s bumper stickers, says she always knew Barack was destined for great things. “My mom and I had a joke that he would become the first black president,” she told NEWSWEEK. “He was so smart, but also wise beyond his years. He had so commanding a presence. He was like a little big man. We called him ‘the little big man,’ because in many ways he was an old man when he was a kid.”

About a decade younger than Obama, she has those familiar wide-set eyes, the generous grin, the measured speaking cadence. They share a mother, Ann Dunham. They share, too, the absence of a father. Her father, an Indonesian business executive, and her mother divorced not long after Soetoro-Ng was born. Obama also grew up without knowing his father, Barack Obama Sr., who returned to his native Kenya. Even by the multicultural standards of Hawaii, the half-siblings grew up knowing their home was scarcely the social norm, with strands connecting Kansas, Kenya and Jakarta. Soetoro-Ng says that Barack helped her sift through those complexities. “He really took over a great many of the responsibilities of raising me,” she says—crediting her brother with introducing her to the works of Toni Morrison and James Baldwin (in his book “Dreams of My Father” Barack recalls scolding Soetoro-Ng for watching TV and neglecting the stack of books he’d given her)—and taking her through the streets of Chicago and New York. They spent summers together in Honolulu, Chicago and Somerville, Mass.

Soetoro-Ng plans to fly from her home in Honolulu to Chicago and then strike out for such key early states as Iowa, New Hampshire and South Carolina. It’s her first real foray into politics—though she admits bashfully to taking part in some protest marches as a teenager. Don’t look to Soetoro-Ng to help Obama start throwing punches, as he’s promised, at his rivals. Her motherly sensibilities seem far afield from the instinct for the political jugular. Requests to engage on even mildly controversial topics in the campaign are politely rebuffed. The toughest thing she’d say about her sibling? “He could be bossy, but he was never mean. He still is.”