Navigating evidence, legitimacy, and delivery: a three-dimensional framework for behavioral policy design

Behavioral public policy faces the triple challenge of assembling robust evidence, securing democratic legitimacy, and navigating implementation constraints. We introduce a three-dimensional policy cube that positions interventions along evidence robustness (E), policy contestation (C), and implementation feasibility (F). Linking each axis to the Capability–Opportunity–Motivation (COM-B) model grounds the cube in behavioral theory, while equity-sensitive scoring captures distributional and administrative-burden effects. We use COM-B as a mechanism-first heuristic for anticipating which governance constraint is likely to be most binding for a given intervention, while recognizing that most real policies load onto multiple COM-B components and therefore multiple cube axes. To support reproducible placement, we provide a transparent scoring rubric (with a worked example) for assigning E, C, and F coordinates. To demonstrate its analytic value, we run a Monte Carlo simulation of fifty stylized interventions over five years. True effects are drawn from a bimodal distribution; replication precision tightens with evidence robustness, backlash probability, and severity rise with contestation, and fidelity decays as a function of feasibility. The cube synthesizes behavioral science, implementation research, and political economy in a single diagnostic, yielding governance templates that range from fast-tracking technocratic sweet spots to sandboxing high-risk (“zombie”) policies. It provides researchers with a measurement agenda, practitioners with a portfolio tool, and policymakers with an adaptive oversight guide.