Rear Parking light doesn't work

[dwil]

The rear drivers parking light doesn't work.
Brake light works fine.
Bulb is good.
Fuse is good.

Swapped light socket with passenger side, good.
Put passenger side to drivers, no good.

Bought new wiring blade/socket.

Still no good.

Took bare wires, touched them while the parking lights were on... and viola it works. Turn off lights, attach wires, turn light on... no worky.

It seems to be that the switch isn't able to turn the bulb on for parking anymore. Is it the switch or a relay? What should I try?