Representative William J. Jefferson has always liked to talk about growing up in an impoverished farm community, picking cotton for $3 a day and hitting the books hard enough to win his ticket out — a scholarship to Harvard Law School. But even as Mr. Jefferson built a reputation as one of Louisiana's brightest, most effective leaders, a less flattering view began to emerge, one signified by his nickname in political circles, "Dollar Bill." Early in his career, as a state legislator, he was criticized for enriching his law firm with contracts from state and local agencies. He also ran...