This article presents a method for analyzing the extent and strength of coattail voting in presidential elections. This method allows the authors to estimate the magnitude of coattail voting and then to decompose this estimate into more “basic” elements. Estimates are given for presidential elections beginning with 1956.
The determination of the coattail vote and its decomposition depend on the theory of the voting decision that is assumed. In this article we present a model of vote determination that is similar in most respects to the traditional SRC model; the vote for congressional representation in a presidential election year is determined jointly by partisan affiliation, attitudes toward the presidential candidates, and local forces unique to the congressional race (such as may be captured by an incumbency variable). This model permits the separate estimation of the strength of short-term forces and of the efficiency of the presidential coattails.
Application of the model to survey data since 1956 indicates that efficiency of presidential coattails has declined during this period. Furthermore, the 1980 election does not appear to be an exception to this trend. On the other hand there has not been any particular trend in the strength of short-term forces during this period; instead events peculiar to the context of a specific election generate short-term forces at the level of the presidential election, but the degree to which these forces are carried over to local races seems to have declined.