When it comes to vote choice, research has generally suggested little impact from watching debates. Debate viewers tend to be among the most politically engaged and thereby likely to have their minds made up well before the debate. For these people, debates serve largely as a spectator sport...
However, research into potential indirect effects of debates — by commanding significant media attention in the days prior to and after their occurrence — have offered stronger evidence of their influence. One such effect involves learning, whereby voters make gains in their understanding of the issues and candidates after the debates. But while more knowledgeable voters tend to learn more from viewing the actual debates, less knowledgeable voters have been shown to narrow this gap in the days following debates due to debate-related content being hard to avoid even among those who are the least politically engaged.