Among the moneyed du Ponts, who preferred the privacy of their elegant homes and the offices and plants of the chemical company that bore their name, Pierre S. “Pete” du Pont IV was a bit of a rebel. Du Pont, who died Saturday at age 86 after a long illness, according to his former chief of staff, broke with family tradition by leaving the family business for a career in law and politics. That led du Pont to multiple elected offices and an unsuccessful bid in the 1987-88 Republican presidential primary race.