  We use the dynamical cluster approximation to understand the proximity of the
superconducting dome to the quantum critical point in the two-dimensional
Hubbard model. In a BCS formalism, $T_c$ may be enhanced through an increase in
the d-wave pairing interaction ($V_d$) or the bare pairing susceptibility
($\chi_{0d}$). At optimal doping, where $V_d$ is revealed to be featureless, we
find a power-law behavior of $\chi_{0d}(\omega=0)$, replacing the BCS log, and
strongly enhanced $T_c$. We suggest experiments to verify our predictions.
