  Spectropolarimetry is a powerful tool to investigate the central regions of
active galactic nuclei (AGNs) as polarization signatures are key to probing
magnetic field structure, evolution, and the physics of particle acceleration
in jets. Optical linear polarization of blazars is typically greater than a few
percent, indicating the emission is dominated by nonthermal synchrotron
radiation, while polarization less than a few percent is common for other type
1 AGNs. We present a spectropolarimetric study of PKS 0637-75 and PKS 1510-089
to determine how the head-on orientation of a jet and dominant emission
processes influence polarimetric variations in the broad lines and continuum.
Observations were obtained biweekly from the Robert Stobie Spectrograph on the
Southern African Large Telescope. Variability in the continuum polarization is
detected for both PKS 0637-75 and PKS 1510-089, with a total average level of
2.5% +/- 0.1% and 7.5% +/- 0.1%, respectively. There is no clear polarization
in the broad Balmer emission lines and weak polarization in Mg II as the
average level across all observations is 0.2% +/- 0.1% for Hbeta, 0.2% +/- 0.3%
for Hgamma, and 0.6% +/- 0.2% for Mg II. We find that polarization measurements
confirm the conclusions drawn from spectral energy distribution modeling of the
disk-jet contributions to the emission as optical polarization and time
variability for PKS 0637-75 are shown to be dominated by accretion disk
emission while those of PKS 1510-089 are due to both disk and jet emission,
with greater jet contribution during flaring states.
