Positive theories of congressional parties

In recent years, positive theories of congressional parties have been elabo rated to encompass a variety of institutional features. The seasoning of th e field is reflected in its contrasting theoretical accounts of the existen ce of parties and their effects, and the return to empirical evidence in a set of insightful studies of modern congressional decision making. This pap er provides a critical review of this recent literature and suggests some u nfinished tasks in the development of this field.