To understand modern Republican thinking on fiscal policy, we need to go back to perhaps the most politically brilliant (albeit economically unconvincing) idea in the history of fiscal policy: “supply-side economics”. Supply-side economics liberated conservatives from any need to insist on fiscal rectitude and balanced budgets. Supply-side economics said that one could cut taxes and balance budgets, because incentive effects would generate new activity and so higher revenue.
The political genius of this idea is evident. Supply-side economics transformed Republicans from a minority party into a majority party. It allowed them to promise lower taxes, lower deficits and, in effect, unchanged spending. Why should people not like this combination? Who does not like a free lunch?
Martin Wolf, The Financial Times