  We present multi-epoch spectral and spectropolarimetric observations of the
Type IIn supernova (SN) 1997eg that indicate the presence of a flattened
disk-like concentration of circumstellar material surrounding nonspherical
ejecta, with which the disk is misaligned. The polarization across the broad H
alpha, H beta, and He I 5876 lines of SN 1997eg forms closed loops when viewed
in the Stokes q-u plane. Such loops occur when the geometrical symmetry of one
or both of the Stokes parameters across spectral lines is broken, in this case
most likely by occultation of the ejecta by the equatorial circumstellar matter
concentration. The polarization of the narrow Balmer lines possesses an
intrinsic axis that differs by 12 degrees from that of the elongated ejecta and
probably indicates the orientation of the disk-like circumstellar material. The
existence of two different axes of symmetry in SN 1997eg suggests that neither
rotation of the progenitor nor the influence of a companion star can be the
sole mechanism creating a preferred axis within the supernova system. Our model
supports the emerging hypothesis that the progenitors of some Type IIn
supernovae are luminous blue variable stars, whose pre-supernova mass eruptions
form the circumstellar shells that physically characterize the SN IIn subclass.
These conclusions, which are independent of interstellar polarization effects,
would have been unobservable with only a single epoch of spectropolarimetry.
