Author: (NBER) The National Bureau of Economic Research: Gautam Gorwrisankaran, Mathew F. Mitchell and Andrea Moro
Date: September, 2004
Quick Facts
- Between 1914 and 2004, Incumbent U.S. senators running for reelection have won nearly 85% of the time.
- Incumbents face weaker challengers than in open seat elections.
USTL Takeaway: Since 1914, incumbent U.S. senators running for reelection have won almost 80% of the time. We investigate why incumbents win so often. We allow for three potential explanations for the incumbency advantage: selection, tenure, and challenger quality, which are separately identified using histories of election outcomes following an open seat election. We specify a dynamic model of voter behaviour that allows for these three effects, and structurally estimate the parameters of the model using U.S. Senate data. We find that tenure effects are negative or small. We also find that incumbents face weaker challengers than candidates running for open seats. If incumbents faced challengers as strong as candidates for open seats, the incumbency advantage would be cut in half.” *for the sake of brevity, this is not an official summary ready to be published from USTL and is instead the executive summary written by NBER themselves*
“Note that the selection effect still implies that incumbent senators are hard to defeat, and therefore our finding that potential challengers might be dissuaded from running against incumbents is not puzzling.”