It’s Nothing Personal: The Decline of the Incumbency Advantage in US House Elections

With little fanfare, the electoral advantage enjoyed by US representatives has fallen over the past several elections to levels not seen since the 1950s. The incumbency advantage has diminished in conjunction with an increase in party loyalty, straight-ticket voting, and president-centered electoral nationalization, products of the widening and increasingly coherent partisan divisions in the American electorate. Consequently, House incumbents now have a much harder time retaining districts that lean toward the rival party. Democrats had been the main beneficiaries of the denationalization of electoral politics that had enabled the incumbency advantage to grow, and they have thus been the main victims of the reemergence of a more party-centered electoral process. Republicans enjoy a long-standing structural advantage in the distribution of partisans across districts, so this trend has strengthened their grip on the House even as they have become less competitive in contests for the presidency.