We study the effect of televised broadcasts of floor debates on the rhetoric and behavior of U.S. Congress Members, focusing on a measure of emotionality, relative to rationality, constructed using computational linguistics methods. First, we show in a differencesin-differences analysis that the introduction of C-SPAN broadcasts in 1979 increased the use of emotional appeals in the House relative to the Senate, where televised floor debates were not introduced until later. Second, we use exogenous variation in C-SPAN channel positioning as an instrument for C-SPAN viewership by Congressional district, and show that House Members from districts with higher C-SPAN viewership are more emotive, rather than deliberative, in floor debates. Contra accountability models of transparency, C-SPAN has no effect on measures of legislative effort on behalf of constituents, and if anything it reduces a politician’s constituency orientation. We find that local news coverage – that is, mediated rather than direct transparency – has the opposite effect of C-SPAN, increasing legislative effort but with no effect on emotional rhetoric. Looking to electoral pressures as a mechanism, we find the emotionality effect of C-SPAN is strongest in competitive districts. Finally, C-SPAN exposure increases the incumbency advantage, and the incumbency effect is much larger among Congress Members who speak emotionally. These results highlight the importance of audience and mediation in the political impacts of higher transparency.