The logic of self-interest was nothing new. Machiavelli’s 16th-century treatise “The Prince” detailed cynical rules of statecraft to extend political power. Thomas Hobbes, in his 17th-century book “Leviathan,” held that aggressive, self-serving acts were “natural” unless forbidden by law. Adam Smith’s “The Wealth of Nations,” published in 1776, noted that people pursuing their own good also produced benefits for society at large.

But Dr. Buchanan contended that the pursuit of self-interest by modern politicians often led to harmful public results. Courting voters at election time, for example, legislators will approve tax cuts and spending increases for projects and entitlements favored by the electorate. This combination can lead to ever-rising deficits, public debt burdens and increasingly large governments to conduct the public’s business.

Indeed, he said, governments had grown so vast and complex that it was no longer possible for elected officials to make more than a fraction of the policy decisions that genuinely affect the people. Thus, he said, much discretionary power is actually held by civil functionaries who can manipulate priorities, impose barriers to entitlements and pressure legislators for rules and budgets favorable to their own interests.

Dr. Buchanan did not invent the theory of public choice, an idea whose origins are obscure but that arose in modern economics literature in the late 1940s. But from the 1950s onward, he became its leading proponent, spearheading a group of economists in Virginia that sought to change the nature of the political process, to bring it more into line with what the group considered the wishes of most Americans.

In lectures, articles and more than 30 books, Dr. Buchanan amplified on the theory of public choice and argued for smaller government, lower deficits and fewer regulations — a spectrum of policy objectives that were ascendant in the 1980s conservative agenda of President Ronald Reagan.