This article examines how emotional reactions to political events shape public opinion. We analyze political discussions in which people voluntarily engage online to approximate the public agenda: Online discussions offer a natural approach to the salience of political issues and the means to analyze emotional reactions as political events take place in real time. We measure shifts in emotions of the public over a period that includes 2 U.S. presidential elections, the 9/11 attacks, and the start of military action in Afghanistan and Iraq. Our findings show that emotional reactions to political events help explain approval rates for the same period, which casts novel light on the mechanisms that mediate the association between agenda setting and political evaluations.