  The orbital period of the hot Jupiter WASP-12b is apparently changing. We
study whether this reflects orbital decay due to tidal dissipation in the star,
or apsidal precession of a slightly eccentric orbit. In the latter case, a
third body or other perturbation would be needed to sustain the eccentricity
against tidal dissipation in the planet itself. We have analyzed several such
perturbative scenarios, but none is satisfactory. Most likely therefore, the
orbit really is decaying. If this is due to a dynamical tide, then WASP-12
should be a subgiant without a convective core as Weinberg et al. (2017) have
suggested. We have modeled the star with the MESA code. While no model fits all
of the observational constraints, including the luminosity implied by the GAIA
DR2 distance, main-sequence models are less discrepant than subgiant ones.
