What can cause our ignition switch to not turn over with key in it

What can cause our ignition switch to not turn over with key in it Hi fellas, we recently bought a 1988 Chevrolet G20 camper Van and we were having to wiggle the key to get the ignition to turn over but once we get it to turn it cranks just fine. Today, after trying for hours, we can’t get it to turn over, we tried turning the wheel, we tried getting a new key thinking the key was worn out but it still won’t turn over now. Any ideas on what it could be?