Promise making is at the heart of democratic politics. Candidates make campaign promises to win elections. Elected officials enter into commitments with one another, and with interest groups, during the process of governing. And committing the government to a particular policy vision is central to both party and regime building. Yet, while promises are rooted in the imperatives of democratic life, they nonetheless pose a serious political dilemma for democracy. Without the ability to endow policies with durability, officeholders cannot shape the future of the polity. If every governmental promise is written in stone, leaders will eventually lose the capacity to control the present. How politicians manage and manipulate this fundamental tension between commitment and flexibility is the subject of this book.

As the empirical material for this investigation, the book explores the origins and evolution of an important yet little-studied institutional arrangement – trust funds in the United States national budget. Major examples include the Social Security Trust Fund, the Medicare Hospital Insurance Trust Fund, and the Highway Trust Fund. In contrast to general revenues, which are available for the general purposes of government, trust funds are “restricted by law to designated programs or uses.” The funds obtain most of their revenues from specific earmarked taxes (e.g., payroll taxes and gasoline taxes). Certain trust funds, however, also receive transfers from within the budget, such as interest payments into the Social Security Trust Fund.