  We re-examine the differences observed in the pc-scale magnetic field
geometry of high and low optical polarization Quasars (HPQs, LPRQs) using the
MOJAVE sample. We find that, as previously reported, HPQ jets exhibit
predominantly transverse B fields while LPRQ jets tend to display longitudinal
B fields. We attempt to understand these results along with the different B
field geometry observed in the low and high energy peaked BL Lacs (LBLs, HBLs)
using a simple picture wherein the spinning central black holes in these AGNs
influence the speed and strength of the jet components (spine, sheath). Higher
spin rates in HPQs compared to LPRQs and LBLs compared to HBLs could explain
the different total radio powers, VLBI jet speeds, and the observed B field
geometry in these AGN classes.
