The Incumbency Advantage in the US Congress: A Roller-Coaster Relationship

While every student in American politics knows that the incumbency advantage grew post-1965, it is less clear as to whether or not this growth has been sustainable throughout the 1980s, 1990s and 2000s. Focusing on the last three decades, we show that the electoral margins of sitting members of the House of Representatives have not linearly grown over the past 60 years. On the contrary, the constant increase in incumbents' vote shares between the 1960s and 1980s could not be sustained in the 1990s. In fact, in the 1990s, the incumbency advantage dropped sharply to levels experienced in the 1960s. In recent years, the electoral margin of sitting House members seems to have grown again to levels comparable to those in the 1970s.