… is from page 113 of my late Nobel-laureate James Buchanan’s “Constraints on Political Action,” which is chapter 3.1 in James M. Buchanan and Richard A. Musgrave, Public Finance and Public Choice: Two Contrasting Visions of the State (1999):
As they must operate, government agents can, at best, represent the interests of the members of the coalition whose support placed them in positions of authority. In the absence of nonelectoral constraints [such as those imposed by constitutions], those agents will, naturally, discriminate in favor of their supporters and against those who supported others. Nondiscriminatory action will be dominated by discriminatory action and for whomever makes up the relevant ruling coalition.