The transition zones between strong and weak tropical land region convection (hereafter, "convective margins") are characterized by considerable interannual and lower-frequency precipitation variability. Given that simulations frequently indicate strong sensitivity of convective margins to projected future climate change, a detailed mechanistic understanding of them is crucial. The simple convective margin prototype previously developed by the authors considered how various large-scale dynamic and thermodynamic factors (e.g., low-level wind speed, inflow humidity) control where precipitation occurs over tropical continents. Here, extension of the convective margin prototype to include impacts of soil moisture is considered. Overall, inclusion of soil moisture increases the variability of the convective margin, although the manner in which it does so is nontrivial. For example, under perturbations to the low-level wind field, the presence of soil moisture imparts an asymmetry to displacements of the convective margin, with a given amplitude of anomalous inflow into the convecting region producing smaller shifts than anomalous outflow of the same magnitude. Predictions of the margins prototype are broadly supported by simulations using an intermediate level complexity model; in fact, the prototype facilitates interpretation of diagnostics such as precipitation variance budgets. Viewing soil moisture impacts through the lens of convective margins may offer insights into the feedback between soil moisture and precipitation and the phenomenon of soil moisture-precipitation coupling "hotspots."