  Accreting, steadily nuclear-burning white dwarfs are associated with
so-called close-binary supersoft X-ray sources (SSSs), observed to have
temperatures of a few$\times 10^{5}$K and luminosities on the order of
$10^{38}$erg/s. These and other types of SSSs are expected to be capable of
ionizing their surrounding circumstellar medium, however, to date only one such
nebula was detected in the Large Magellanic Cloud (of its 6 known close-binary
SSSs), surrounding the accreting, nuclear-burning WD CAL 83. This has led to
the conclusion that most SSSs cannot have been both luminous ($\gtrsim
10^{37}$erg/s) and hot ($\gtrsim$ few $\times 10^{4}$K) for the majority of
their past accretion history, unless the density of the ISM surrounding most
sources is much less than that inferred for the CAL 83 nebula
(4--10$\rm{cm}^{-3}$). Here we demonstrate that most SSSs must lie in much
lower density media than CAL 83. Past efforts to detect such nebulae have not
accounted for the structure of the ISM in star-forming galaxies and, in
particular, for the fact that most of the volume is occupied by low density
warm \& hot ISM. CAL 83 appears to lie in a region of ISM which is at least
$\sim 40$-fold overdense. We compute the probability of such an event to be
$\approx 18\%$, in good agreement with observed statistics. We provide a
revised model for the "typical" SSS nebula, and outline the requirements of a
survey of the Magellanic clouds which could detect the majority of such
objects. We then briefly discuss some of the possible implications, should
there prove to be a large population of previously undiscovered ionizing
sources.
