  Using the renormalon calculus, we study the asymptotic behavior of the
perturbative expansion of the hard-scattering kernels entering the QCD
factorization formula for the nonleptonic weak decays B->D M, where M is a
light meson. In the ``large-beta_0 limit'', the kernels are infrared finite and
free of endpoint singularities to all orders of perturbation theory. The
leading infrared renormalon singularity corresponding to a power correction of
order Lambda/m_b vanishes if the light meson has a symmetric light-cone
distribution amplitude. We calculate the Borel transforms and the corresponding
momentum distribution functions of the hard-scattering kernels, and resum the
series of O(beta_0^{n-1} alpha_s^n) corrections to explore the numerical
significance of higher-order perturbative and power corrections. We also derive
explicit expressions for the O(beta_0 alpha_s^2) contributions to the kernels,
and for the renormalon singularities corresponding to power corrections of
order (Lambda/m_b)^2. Finally, we study the limit m_c->0 relevant to charmless
hadronic decays such as B->pi pi.
