  In the JWST, Extremely Large Telescopes, and LUVOIR era, we expect to
characterize a number of potentially habitable Earth-like exoplanets. However,
the characterization of these worlds depends crucially on the accuracy of
theoretical models. Validating these models against observations of planets
with known properties will be key for the future characterization of
terrestrial exoplanets. Due to its sensitivity to the micro- and macro-physical
properties of an atmosphere, polarimetry will be an important tool that, in
tandem with traditional flux-only observations, will enhance the capabilities
of characterizing Earth-like planets. In this paper we benchmark two different
polarization-enabled radiative-transfer codes against each other and against
unique linear spectropolarimetric observations of the earthshine that cover
wavelengths from $\sim$0.4 to $\sim$2.3 $\mu$m. We find that while the results
from the two codes generally agree with each other, there is a phase dependency
between the compared models. Additionally, with our current assumptions, the
models from both codes underestimate the level of polarization of the
earthshine. We also report an interesting discrepancy between our models and
the observed 1.27 $\mu$m $O_2$ feature in the earthshine, and provide an
analysis of potential methods for matching this feature. Our results suggest
that only having access to the 1.27 $\mu$m $O_2$ feature coupled with a lack of
observations of the $O_2$ A and B bands could result in a mischaracterization
of an Earth-like atmosphere. Providing these assessments is vital to aid the
community in the search for life beyond the solar system.
