  We present observational evidence for the link between variability of the
radio emission of the relativistic jet and optical continuum emission in the
radio galaxy 3C 390.3 which indicates that the source of variable non-thermal
continuum radiation is located in the innermost part of the relativistic jet.
We suggest that the continuum emission from the jet ionizes material in a
subrelativistic outflow surrounding the jet, which results in a formation of a
conical region with broad emission lines at a distance of about 0.4 parsecs
from the central nucleus.
