  We introduce a McMillan-Ginzburg-Landau theory to describe the cooperative
coexistence of charge-density and superconducting order in two-dimensional
crystals. With a free-energy that explicitly accounts for the competition
between commensurate and incommensurate ground states, we are able to map the
transition between these phases and monitor the development of
discommensurations in the near-commensurate regime. Attributing the enhancement
of superconducting order to density-wave fluctuations, we propose a coupling
scheme that yields a phase diagram in qualitative agreement with experiments in
conducting transition metal dichalcogenides. The model predicts the development
of non-uniform superconductivity similar to that arising from a pair-density
wave, with a spatial texture driven by the underlying charge-density wave
fluctuations.
