Candidate quality and US Senate elections

We find that candidate quality is a key determinant of US Senate election outcomes. We model the results for the last 10 US Senate election cycles, from 2012 back to 1994, for a total of 345 election contests. For the contests where an incumbent seeks re-election, a quality challenger can significantly diminish the advantage that usually attaches to incumbency. For the open-seat contests, which tend to be more competitive, candidate quality can swing a close election. Governors who seek election to the US Senate receive the largest boost, as indicated by our candidate-quality variables vector. Wave effects and presidential coattail effects are also shown to be contributing factors in certain cases.