Legislators and their constituents alike weigh policy alternatives in terms of ideology, about which they disagree, and on the basis of shared public policy values, such as a desire for efficiency. The initial section of this chapter sets forth a simple model of policy preferences that incorporates both sets of considerations, policy position, and what Stokes (1963) referred to as policy “valence,” and it helps to illustrate how the balance individuals strike between them can facilitate or prevent agreement on policy choices.

The second section of this chapter builds on the basic model of the first to analyze an important source of agenda control in legislative politics: the ability to formulate policies that mix controversial ideological departures from the ideological status quo with high valence. This is largely dependent on the ability of policymakers to deploy large expert staffs to help them formulate policy initiatives. In all presidential systems the executive enjoys an advantage on this score, an advantage that is substantial even in the U. S., where Congress is sometimes able to act as a “policy incubator.” In Latin America, where legislatures must cope with very sparse infrastructure, the executive's advantage at formulating high-valence proposals is overwhelming. The ability to formulate high-valence proposals magnifies the executive dominance over the policy agenda that is written into many constitutions, while legislators' influence over the agenda can be severely curbed by their inability to formulate proposals with valence high enough to compete with the status quo.