Originally Posted by Master4th
The Tail Lights are ground through the housing to the body. There are 3 bolts that hold your tail lights on. Those are the grounding bolts as well.
If you are positive that the bulbs are not blown, I will second that^^^^^. Those mounting bolts are the ground for the lights and have to be clean!
You could also check/clean the connections in the wiring harness leading to the tail lights in each corner (looking up into each back corner from the underside). Disconnect, clean, add dielectric grease.
Because the center tail light works, I would doubt the break switch is the issue.