Am I Supposed to See 12V at the Tail Lights?

Thanks to all for your replies. "Upon further review," subject to your edits/corrections . . . it's painfully obvious to me that I screwed up by not referencing the ground wire found inside the lens fixture. As I understand the collective analysis, my error was measuring directly to the positive and negative wires that feed the light bulb socket (I exposed bare wire on each and applied my meter's probes).

If I read correctly, the correct way to analyze DC voltage on that circuit is to measure the positive (hot) wire and the ground wire - not the negative wire. There is a very short, white ground wire that hopefully I can expose for a proper measurement.

Thanks for any course corrections!