(BY ANNE BLYTHE, Staff writer) John Edwards has asked a judge in state court to postpone a question-and-answer session he was to have under oath later this month with lawyers involved in the legal wrangle over a videotape that purportedly shows him having sex with his mistress.Edwards, 57, the former senator and former presidential candidate, was indicted in federal court last week, accused of "participating in a scheme to violate federal campaign finance laws." He is accused of improperly using campaign money to keep his extramarital affair out of the public eye as he pursued his bid for the White House.