  We construct spin-improved holographic light front wavefunctions for the
nucleons (viewed as quark-diquark systems) and use them to successfully predict
their electromagnetic Sachs form factors, their electromagnetic charge radii,
as well as the axial form factor, charge and radius of the proton. The
confinement scale is the universal mass scale of light-front holography,
previously extracted from spectroscopic data for light hadrons. With the Dirac
and Pauli form factors normalized using the quark counting rules and the
measured anomalous magnetic moments respectively, the masses of the quark and
diquark are the only remaining adjustable parameters. We fix them using the
data set for the proton's Dirac-to-Pauli form factor ratio, and then predict
all other data without any further adjustments of parameters. Agreement with
data at low momentum-transfer is excellent. Our findings support the idea that
light (pseudoscalar and vector) mesons and the nucleons share a nonperturbative
universal holographic light-front wavefunction which is modified differently by
their spin structures.
