No start by key,but works when jumped.Help!!

Went out to fire up the 66 Dart today,no power to ignition,no lights.Checked all gounds cleaned and put back on,nothing?So I jumped it through the starter relay,it fired up and everything works.Hmm!I traced power into car put isn,t getting any to the ignition.Car started yesterday by the ignition.Could the voltage reg have gone?Or what about the light switch?Everything works when I jump it.HelpAnybody got any suggestions?