The Polarization Effect of Monopsonistic Lobbying

Classical spatial models predict platform convergence, yet empirical polarization persists. This paper proposes a non-electoral mechanism: lobbying as a monopsonistic market for legislative support. Here, extreme benefactors must pay more to attract distant politicians, creating a rent gradient that rewards platform differentiation. We find that the unique equilibrium places politicians at $(\frac{1}{4},\frac{3}{4})$ for any monotone policy-production cost. Thus, polarization can arise solely from lobbying-market structure, independent of electoral incentives.