CHANGING MEANINGS OF ELECTORAL MARGINALITY IN UNITED-STATES-HOUSE ELECTIONS, 1824-1978

Gary Jacobson (1987a, 1987b) has suggested that increased vote proport ions for incumbent House candidates during the 1960s and 1970s have no t resulted in greater electoral safety, primarily because of greater o bserved volatility in interelection vote swings occurring during the s ame era. Using data on House elections from 1824 to 1978, we find that both ''marginal'' and ''safe'' incumbents are much more vulnerable to electoral defeat during the 19th century than during the 20th century . This pattern seems to be explained by greater homogeneity of interel ection vote swings during the 20th century. Overall, our results lend strong support to Jacobson's assertion that the meaning of electoral m arginality varies substantially over time.