  We present a detailed study of the nuclear structure of the highly polarized
broad absorption line quasar, Mrk 231, through a multiwavelength campaign of
Chandra observations, optical spectroscopy, optical spectropolarimetry, and
imaging polarimetry. This campaign was designed to extend the 40 ks Chandra
study of Gallagher et al. and the optical and UV spectropolarimetric study of
Smith et al. to probe variability on multiple time scales. As direct emission
from the nucleus is heavily obscured at optical through X-ray wavelengths, the
detailed study of scattered emission has lead to insights into the stratified
and complex central region of this active galaxy. Though significant continuum
variability is not detected in any of the three new 40 ks Chandra observations,
we investigate FeKalpha emission features in the individual and combined
spectra. Comparing echelle spectra of the NaI D absorption lines with the
literature, we show that one system disappeared in 2000 only to reappear in
later epochs. Notably, we detect a large decrease in polarization across the
entire optical spectrum of Mrk 231 from 1995 to 2003. Though the polarization
fraction fell, e.g., from 4% to 3% at about 6000 Angstroms, the polarization
position angle spectrum remained unchanged. The optical polarization behavior
is consistent with a decrease in the flux scattered by circumnuclear material
on spatial scales where the broad-line region is resolved by the scattering
material. Ultraviolet imaging polarimetry of Mrk 231 by HST sets an upper limit
on the distance between the active nucleus and the scattering regions of <20
pc.
