Evidence for a scale invariant relationship between the incumbency advantage and the nationalization of US House elections 1866-2014

In a recent article, Jacobson examines the rise and fall of the incumbency advantage from 1952 to 2014. He shows that the incumbency advantage over this period rose as elections became more localized, and has fallen in recent decades as elections have become more nationalized. In this research note, we examine whether a similar relationship holds when we extend the time-series back to the end of the Civil War. Consistent with earlier work, we find that the scale of the incumbency advantage was much smaller in the period prior to 1952-approximately ranging between 0 and 4 points. However, despite this difference in scale, there remains a very similar negative correlation between the nationalization of elections and the incumbency advantage. We therefore speculate that the nationalization of elections diminishes the relative size of the incumbency advantage, but the overall size of that advantage may also be shaped by other factors, such as technology, institutional reforms, or changes in the media landscape.