MANNING, S.C. — Alvin Greene earned the nickname "turtle" in high school – a quiet, withdrawn boy who was smart when he applied himself but rarely took a chance and tried to put himself in comfortable situations.

Nearly four weeks ago, the 32-year-old unemployed military veteran turned South Carolina's political scene upside down when he won the Democratic nomination for a U.S. Senate seat. And unlike that high school student, he's taking a big chance: running against powerhouse Republican Sen. Jim DeMint.

He is remembered as painfully shy by those who knew him in high school, where Greene was the only black person on the tennis team. His mother died of cancer when he was a boy; a brother died of cystic fibrosis. The few people who know him say the man with a political science degree from the University of South Carolina is smarter than his national image suggests.