  We study the suppression of the small-scale power spectrum due to the decay
of charged matter to dark matter prior to recombination. Prior to decay, the
charged particles couple to the photon-baryon fluid and participate in its
acoustic oscillations. However, after decaying to neutral dark matter the
photon-baryon fluid is coupled only gravitationally to the newly-created dark
matter. This generically leads to suppression of power on length scales that
enter the horizon prior to decay. For decay times of approximately 3.5 years
this leads to suppression of power on subgalactic scales, bringing the observed
number of Galactic substructures in line with observation. Decay times of a few
years are possible if the dark matter is purely gravitationally interacting,
such as the gravitino in supersymmetric models or a massive Kaluza-Klein
graviton in models with universal extra dimensions.
