  Context. An optically thick, geometrically thin accretion disk (AD) around a
supermassive black hole might contribute to broad-line emission in type-1
active galactic nuclei (AGN). However, emission line profiles are most often
not immediately consistent with the profiles expected from a rotating disk. The
extent to which an AD in AGN contributes to the broad Balmer lines and
high-ionization UV lines in radio-loud (RL) AGN needs to be investigated. Aims.
This work aims to address whether the AD can account for the double-peaked
profiles observed in the Balmer lines (H$\beta$, H$\alpha$), near-UV
(Mgii$\lambda$2800), and high-ionization UV lines (Civ$\lambda$1549,
Ciii]$\lambda$1909) of the extremely jetted quasar 3C 47. Methods. The low
ionization lines (LILs) (H$\beta$, H$\alpha$, and Mgii$\lambda$2800) were
analyzed using a relativistic Keplerian AD model. Fits were carried out
following Bayesian and multicomponent non-linear approaches. The profiles of
prototypical high ionization lines (HILs) were also modeled by the contribution
of the AD, along with fairly symmetric additional components. Results. The LIL
profiles of 3C 47 are in very good agreement with a relativistic Keplerian AD
model. The disk emission is constrained between $\approx$ 100 and $\approx$
10000 gravitational radii, with a viewing angle of $\approx$30 degrees.
Conclusions. The study provides convincing direct observational evidence for
the presence of an AD and explains the HIL profiles are due to disk and failed
wind contributions. The agreement between the observed profiles of the LILs and
the model is remarkable. The main alternative, a double broad line region
associated with a binary black hole, is found to be less appealing than the
disk model for the quasar 3C 47.
