International Journal of Public Opinion Research Vol. No. ß The Author . Published by Oxford University Press on behalf of The World Association for Public Opinion Research. All rights reserved. doi:./ijpor/edr Advance Access publication November Social Networks that Matter: Exploring the Role of Political Discussion for Online Political Participation Sebastia ´n Valenzuela , Yonghwan Kim and Homero Gil de Zu ´n ˜iga School of Communications, Catholic University of Chile, Santiago, Chile, and School of Journalism, University of Texas at Austin, USA Abstract We examine the relationship between citizen-to-citizen discussions and online political participation considering various attributes of individuals’ social networks: Modality, discussants’ ties, diversity of opinions, and quality of argumentation. Using a national survey of U.S. residents we find that communication within networks is a significant predictor of web-based forms of political engagement, after controlling for offline participation, political orientations, news use, and socio-demographics. Consistent with the ‘‘strength of weak ties’’ argument, larger online networks and weak-tie discussion frequency are associated with online participation. While like-minded dis- cussions are positively related to online participation, discussions with people who are not of like mind correlate negatively with it. Online network size and reasoning discussions were positively related to online participation, although these associations were rather weak compared to the role of other network characteristics. Whereas the idea that ‘‘conversation is the soul of democracy’’ (Kim, Wyatt, & Katz, , p. , emphasis theirs) has resonated for centuries (e.g., de Tocqueville, /), only in the last few decades researchers have accu- mulated strong empirical evidence showing how informal discussions spur political engagement. Discussions create opportunities to learn mobilizing information, ponder about news or public issues, and reach common under- standings, all of which are key antecedents of participation. Most of the existing literature, however, has focused on traditional forms of political engagement—forms that take place face-to-face or in offline settings such as All correspondence concerning this article should be addressed to Sebastia ´n Valenzuela, PhD, School of Communications, Catholic University of Chile, Alameda 340, Santiago, Chile. E-mail: savalenz@uc.cl at Pontificia Universidad Católica de Chile on July 16, 2012 http://ijpor.oxfordjournals.org/ Downloaded from