Thanks for the advice, Doc.

My guess is that it has to be ATF coming from the pump, since the rear of the pulley is coated with oil. What throws me again, though, is that the oil is black, not red.

I still have to suspect that the front seal is leaking because (1) the other pulleys and belts are clean, (2) the coil and vacuum lines on the driver's side fender are coated with the same residue, (3) the rest of the engine is clean, (4) my power steering fluid is a little low, and (5) the steering box isn't leaking. Ergo, the front (and maybe the rear) pump seals must be leaking

Thanks again for the input.