  A gauge invariant method for the investigation of scalar diquark clustering
in the nucleon ground state is presented. The method focuses on a comparison of
quark distributions in the nucleon with those in the $\Delta$ baryon resonance.
Recent lattice QCD calculations of these quark distribution radii are analyzed
in a search for evidence of scalar diquark clustering. The analysis indicates
the lattice results describe the negative squared charge radius of the neutron
with little resort to hyperfine clustering between $u$-$d$-quark pairs. This
result contrasts both quark-diquark and nonrelativistic quark models where
hyperfine attraction between $u$ and $d$ quarks in the nucleon is argued to
play a significant role. Comparison of light quark distributions in $\Lambda^0$
and $\Sigma^{*0}$ indicate only a small reduction of the scalar diquark
distribution radius relative to the vector diquark distribution. Current
lattice QCD determinations of baryon charge distributions do not support the
concept of substantial $u$-$d$ scalar diquark clustering as an appropriate
description of the internal structure of the nucleon.
