[Replication] A Sound Model with One Contained Slip: Formally Replicating Veto Players and Policy Development

Abstract. This paper formally replicates Hirsch and Shotts, "Veto Players and Policy Development" (American Journal of Political Science, 2026; DOI 10.1111/ajps.70046), a model of endogenous policy development under veto players. Fifteen claim-groups were checked across three independent passes — algebra, logic, notation — plus symbolic and numeric corroboration. Eleven verify cleanly, three carry scope qualifications, and one descriptive equilibrium-utility closed form (Proposition C.1) is numerically wrong by exactly (8x_E²/3α)·Š²(1−Š): serious in the original but contained in consequence, propagating to no theorem. The equilibrium characterization and every directional and welfare headline survive. The replication's transferable contribution is the blind rebuild: an independent zero-context modeler, given only the abstract and introduction, reconstructed every primitive and comparative-static sign, certifying the framing as forced by the question rather than chosen to manufacture the result. Verdict: verified, with one published closed form corrected and its consequence contained.