  We present the results of an investigation into the X-ray properties of
radio-intermediate and radio-loud quasars (RIQs and RLQs, respectively). We
combine large, modern optical (e.g., SDSS) and radio (e.g., FIRST) surveys with
archival X-ray data from Chandra, XMM-Newton, and ROSAT to generate an
optically selected sample that includes 188 RIQs and 603 RLQs. This sample is
constructed independently of X-ray properties but has a high X-ray detection
rate (85%); it provides broad and dense coverage of the l-z plane, including at
high redshifts (22% of objects have z=2-5), and it extends to high
radio-loudness values (33% of objects have R*=3-5, using logarithmic units). We
measure the "excess" X-ray luminosity of RIQs and RLQs relative to radio-quiet
quasars (RQQs) as a function of radio loudness and luminosity, and parameterize
the X-ray luminosity of RIQs and RLQs both as a function of optical/UV
luminosity and also as a joint function of optical/UV and radio luminosity.
RIQs are only modestly X-ray bright relative to RQQs; it is only at high values
of radio-loudness (R*>3.5) and radio luminosity that RLQs become strongly X-ray
bright. We find no evidence for evolution in the X-ray properties of RIQs and
RLQs with redshift (implying jet-linked IC/CMB emission does not contribute
substantially to the nuclear X-ray continuum). Finally, we consider a model in
which the nuclear X-ray emission contains both disk/corona-linked and
jet-linked components and demonstrate that the X-ray jet-linked emission is
likely beamed but to a lesser degree than applies to the radio jet. This model
is used to investigate the increasing dominance of jet-linked X-ray emission at
low inclinations.
