It is commonly argued that a presidential candidate will be helped in a state by having a governor of the same party in office. However, there is little research to support this claim. To address this question, we use a regression discontinuity design, which allows us to estimate the causal effect of gubernatorial party control. We show that a presidential candidate is in fact hurt by having a governor from the same party. On average, this penalty is a 3–4 percentage point reduction in a state’s presidential vote share in the following election. We also show that voters punish the presidential party in gubernatorial midterm elections. Having established these relationships, we explore why this is the case. The likely explanation is a variation of the ideological balancing argument, whereby voters’ choices for one office are conditional on which party holds office at a different level.
Erikson, Robert S., Olle Folke och James M. Snyder, Jr. (2015),
"A Gubernatorial Helping Hand? How Governors Affect Presidential Elections".
Journal of Politics