  Missing from the usual considerations of nuclear burning white dwarfs as Type
Ia supernova progenitors are systems with very higher mass transfer rates,
where more material than is needed for steady burning accretes on the white
dwarf. This will move out the photosphere of the white dwarf, causing it to
emit at longer wavelengths. Thus, we propose the name ultra-soft source (USS)
for these objects.
  We present a VLT/FLAMES survey looking for USS in the SMC, selected to be
bright in the far UV and with blue far UV-V colors. While we find some unusual
objects, and recover known planetary nebula and WR stars, we detect no objects
with strong He II lines, which should be a signature of USS. This null result
either puts an upper limit on the number of USS in the SMC, or shows that we do
not understand what the optical spectra of such objects will look like.
  We also discuss the unusual LMC [WN] planetary nebula LMC N66 as a possible
example of an USS. It has a luminosity consistent with that expected, and its
spectra show incompletely CNO-processed material - strong helium lines, some
hydrogen, enhanced nitrogen and depleted carbon. It also shows periodic
outbursts. USS may resemble N66 in quiescence. However, it lacks a FUV excess,
contrary to our predictions.
