The growth of public opinion measurement in the last 40 years has added a new dimension to the study of presidential behavior. Not only have public evaluations become more newsworthy, but the importance of public support as a resource and determinant of political survival has been enhanced. Recent scholarship on the presidency has documented the value of public support, attempted to identify its major determinants, and speculated about the manner in which presidents might influence these evaluations.
This research is designed to integrate these concerns into a single model and thereby to examine the interdependence between public support as a product of citizen decisions and as a political resource. First, a characterization of the citizen as an evaluator of the president is developed and used to construct an equation of presidential approval. Next, we develop an equation that explains presidential effectiveness in the legislative arena and illustrates the operation of public support as a presidential resource. The public support and legislative effectiveness equations are specified as a simultaneous equation system, estimated, and evaluated. The results of the model are then used to expand the conventional wisdom about the determinants of public support, to examine the consequences of the reciprocal relationship between public support and legislative success, and to generate ex post forecasts of President Reagan's support from 1981 through 1983.