An important influence on a presidential candidate's debating style, the "incumbency factor," has been largely ignored by researchers. An analysis of the argumentative style of incumbents, based on the 1976 and 1980 presidential debates, has isolated three distinguishing characteristics: (1) presidential incumbents tend to avoid extended debate with their opponents; (2) incumbents employ a declarative style of debating, tending to make assertions without evidence or analysis; and (3) incumbents focus on the status quo to the neglect of the future. The analysis also suggests that incumbents' debating styles manifest these qualities because the debate topics focus on their records, because incumbents try to capitalize on their "presidential" status, and because presidents have acquired a preference for arguing from their own authority. The argumentative style of incumbents has proven ineffective in presidential debates for at least three reasons. First, debating calls for well-developed arguments rather than a series of assertions backed with the ethos of the presidency. Second, much of the appeal of a campaign debate is rooted in its conflict. An incumbent who avoids direct debate is unlikely to impress his audience. Third, debates involving incumbents are likely to center on their past record rather than on their vision of the future. The analysis suggests that incumbents who ignore the differences in debating styles between incumbents and challengers do so at great risk to themselves. (RBW)