We report on a phenomenological analysis of all available electron scattering data on ${}^{12}C$ (about 6600 differential cross section measurements) and on ${}^{16}O$ (about 250 measurements) within the framework of the quasielastic (QE) superscaling model (including Pauli blocking). All QE and inelastic cross section measurements are included down to the lowest momentum transfer $q$ (including photoproduction data). We find that there is enhancement of the transverse QE response function ($R_T^{QE}$) and quenching of the QE longitudinal response function ($R_L^{QE}$) at low $q$ (in addition to Pauli blocking). We extract parametrizations of a multiplicative low $q$ “longitudinal quenching factor” and an additive “transverse enhancement” contribution. Additionally, we find that the excitation of nuclear states contribute significantly (up to 30%) to the Coulomb sum rule $SL\left(q\right)$. We extract the most accurate determination of $SL\left(q\right)$ to date and find it to be in disagreement with random phase approximation (RPA) based calculations but in reasonable agreement with recent theoretical calculations, such as “first principle Green's function Monte Carlo.”