The school that applies to political actors the same assumptions economics applies to everyone else: that voters, legislators, regulators and bureaucrats pursue their own interests rather than an abstract public good, and that political outcomes should be explained accordingly. James Buchanan described the programme as politics without romance, and the phrase captures both its analytical discipline and the objection it attracts.
Buchanan and Gordon Tullock's The Calculus of Consent (1962) founded the field, analysing constitutional rules as the outcome of bargaining among people who do not know how they will later be placed. From that starting point came a series of durable concepts: rent-seeking, the expenditure of real resources to capture transfers rather than create value; rational ignorance, the voter's reasonable decision not to research decisions their vote will not determine; concentrated benefits and diffuse costs, which explains why small organised groups routinely defeat larger unorganised ones; and regulatory capture. Mancur Olson's work on collective action and Arrow's impossibility theorem sit alongside it as foundations.
Buchanan's distinctive move was constitutional. Since he expected self-interest at every level, he located the remedy not in better officials but in rules chosen behind sufficient uncertainty about one's own future position that they must be general — an argument that earned the Nobel in 1986 and that reads as a Rawlsian device turned to different ends.
The tradition attracts two serious objections. Empirically, the pure self-interest assumption predicts turnout and much bureaucratic behaviour badly, and the field has had to soften it. Politically, critics argue that an analysis which finds democratic politics inherently corrupt supplies a rationale for insulating decisions from democratic control — a charge pressed polemically in Nancy MacLean's Democracy in Chains and disputed in detail by scholars of Buchanan's work. Elinor Ostrom's Bloomington school stands as the empirical counterweight from within the same broad camp, showing communities solving collective-action problems the theory predicted they could not.