Shares of auto retailers AutoNation (AN) and Group 1 Automotive (GPI) tumbled hard Thursday after they reported disappointing third-quarter results before the open. Lithia Motors (LAD), the highest-rated company in the group, also plunged amid a sector sell-off, even though it reported strong Q3 profit and sales gains late Wednesday. The reports come amid continuing uncertainty prior to national elections next month, sluggish economic growth and