Democracy is in retreat or under pressure worldwide. Even in countries with strong democracies, polarization is increasing, and the public sphere is awash in misinformation and conspiracy theories. Many commentators have blamed social media and the lack of platform governance for these unfortunate trends. I review the evidence for these claims and show how the traditional view that mainstream media are instrumental in setting the political agenda has become superseded by politicians’ power to set their own agenda through social media. I review the growing evidence that all forms of media are a causal factor in shaping a variety of political behaviors, from ethnic hate crimes to compliance with social-distancing measures. I examine the implications of this analysis through the tripartite lens of political advertising, free speech, and government regulations.