  We analyze various theoretical aspects of CP violation in singly Cabibbo
suppressed (SCS) D-meson decays, such as $D \to K K,\pi \pi$. In particular, we
explore the possibility that CP asymmetries will be measured close to the
present level of experimental sensitivity of $O(10^{-2})$. Such measurements
would signal new physics. We make the following points: (i) The mechanism at
work in neutral D decays could be indirect or direct CP violation (or both).
(ii) One can experimentally distinguish between these possibilities. (iii) If
the dominant CP violation is indirect, then there are clear predictions for
other modes. (iv) Tree-level direct CP violation in various known models is
constrained to be much smaller than $10^{-2}$. (v) SCS decays, unlike Cabibbo
favored or doubly Cabibbo suppressed decays, are sensitive to new contributions
from QCD penguin operators and especially from chromomagnetic dipole operators.
This point is illustrated with supersymmetric gluino-squark loops, which can
yield direct CP violating effects of $O(10^{-2})$.
