Tail light stays on

Thanks Trailbeast. It may sound like a classic ground issue but when I ground it with a wire, the bulb gets brighter (like going from tail lights to brake lights). The green wire going to the socket is powered 100% of the time, thats why it's on all the time. I disconnected the harness at the driver kick panel and the green wire is powered going back under the dash. I'm guessing it is contacting a hot wire under the dash somewhere. Does this sound reasonable?