The power and limitations of televised presidential debates: Assessing the real impact of candidate performance on public opinion and vote choice

A growing literature establishes that presidential candidates can help and hurt themselves through their performance in televised debates. Debate performance, however, is a somewhat elusive concept. Voters' post-debate assessments of the participants may be heavily colored by pre-existing attitudes toward candidates, parties, and the incumbent president. This paper attempts to tease out the “true” impact of debate performance, i.e., those times in which the candidates' superiority or inferiority on stage breaks through voters' cognitive filters. We find that debate performance is responsible for only about half of the variance in viewers' assessments of winners and losers; that it is possible to be declared the winner in the post-debate polls based entirely on factors exogenous to the debate itself; and that even a highly successful performance might yield only a narrow win in the post-debate polls. We also present evidence that, when measured properly, debate performance can actually alter candidate preferences.