Two terms of endearment? Incumbent-party performance in US presidential elections

Presidential elections are arguably the most consequential recurring political event in the United States. Understanding the factors that determine their outcomes, therefore, is of substantial importance. One proposed factor pertains to presidential candidates' incumbency status, yet its nature is complex and difficult to study with observational data. In particular, the individual-level mechanisms underlying incumbency effects remain unclear. This study proposes many citizens generally believe that, ceteris paribus, presidents should be afforded two terms. Crucially, such a norm implies that incumbency status possesses an inherent effect, operating independent of other mechanisms that may stem from incumbency. A large, pre-registered survey experiment was therefore employed to isolate the effect of incumbency status on presidential vote choice. The experiment finds strong evidence that one-term incumbent candidates have an inherent advantage against their non-incumbent opponents. The results also clarify that the two-term disadvantage present in observational data is not inherent, and is perhaps better understood simply as the absence of the one-term advantage. The study thus points toward a micro-foundational mechanism underlying incumbent-party performance in presidential elections. Finally, analyses of panel data explore which voters may be systematically inclined to vote based upon the incumbency status of presidential candidates.