2000 Dodge Caravan Ocassional ignition switch issue

I have had ocassional ignition start up problems beginning back at about 75000 miles. The problem was that when the key was turned to the on position the engine would not turn over. A light tap on the key seemed to cure the problem, however, every once in a while it would occur again. Lately the problem has been occurring more often. I have to put heavy pressure on the key while turning it in order to get the ignition to catch and the enging to turn over. It seems to act up more when the car is cold or has been sitting for a while. I replaced the ignition cylinder, but the problem still occurs. Should I replace the ignition switch next or is this problem related to something else?