A federal appeals panel has now refused to halt a judge’s order to block New Jersey’s controversial “county line” ballot design in this year’s Democratic primary pending an appeal of that decision, amid a rapidly approaching deadline to the printing of those ballots. The three-judge panel offered no explanation for the decision Wednesday but set a fast-track schedule for filing briefs in the contested case, pending oral arguments on April 12 at the federal courthouse in Philadelphia. The decision marked the latest development in a lawsuit U.S. Rep. Andy Kim filed to abolish the system — the on…