House Majority Whip James Clyburn came to Newark on Thursday to boost a congressman who usually doesn’t need help at primary time. But this year, Rep. Donald Payne Jr. sought the help of Clyburn and other prominent Democrats to fend off an unusually strong challenge for re-election for a seat he’s held for a decade and his father occupied for 24 years before him. Payne’s opponent, Imani Oakley of Montclair, is a former legislative aide who raised $425,511 through March 18 — 59% of it in donations of $200 or less, enough to go on television and worry the long-time incumbent. “That’s what’s scar…