  Radio-loud quasars (RLQs) are more X-ray luminous than predicted by the
X-ray-optical/UV relation (i.e. $L_\mathrm{x}\propto L_\mathrm{uv}^\gamma$) for
radio-quiet quasars (RQQs). The excess X-ray emission depends on the
radio-loudness parameter ($R$) and radio spectral slope ($\alpha_\mathrm{r}$).
We construct a uniform sample of 729 optically selected RLQs with high
fractions of X-ray detections and $\alpha_\mathrm{r}$ measurements.We find that
steep-spectrum radio quasars (SSRQs; $\alpha_\mathrm{r}\le-0.5$) follow a
quantitatively similar $L_\mathrm{x}\propto L_\mathrm{uv}^\gamma$ relation as
that for RQQs, suggesting a common coronal origin for the X-ray emission of
both SSRQs and RQQs. However, the corresponding intercept of SSRQs is larger
than that for RQQs and increases with $R$, suggesting a connection between the
radio jets and the configuration of the accretion flow. Flat-spectrum radio
quasars (FSRQs; $\alpha_\mathrm{r}>-0.5$) are generally more X-ray luminous
than SSRQs at given $L_\mathrm{uv}$ and $R$, likely involving more physical
processes. The emergent picture is different from that commonly assumed where
the excess X-ray emission of RLQs is attributed to the jets. We thus perform
model selection to comparecritically these different interpretations, which
prefers the coronal scenario with a corona-jet connection. A distinct jet
component is likely important for only a small portion of FSRQs.The corona-jet,
disk-corona, and disk-jet connections of RLQs are likely driven by independent
physical processes. Furthermore, the corona-jet connection implies that
small-scale processesin the vicinity of SMBHs, probably associated with the
magnetic flux/topology instead of black-hole spin, are controlling the
radio-loudness of quasars.
