This thesis aims to contribute to recent discussions in media and cultural studies and political communication about reconceptualising the relationships between politics, media and public engagement. It will do so by articulating the context and processes in which private citizens form political publics and the ways in which media genres beyond conventional news and public affairs encourage or enable civic engagement. It explores these issues in the context of the ongoing democratisation of South Korea since 1987, a nation with a particularly dynamic digital culture. The thesis critiques the conventional binaries between the private (emotion/entertainment/fans) and the public (reason/news/publics), and articulates the mediating contexts and processes in which the private shifts to the public. It seeks to situate affect and entertainment (popular culture) as key agents in mobilising and sustaining citizens' political interest and participation. The key research questions are therefore: in what context do media offer a discursive space to connect people's everyday lives to the public world as well as to recruit and sustain political interest?; how does affect play a critical part in making sense of the public world, and mobilising political participation?; and in what ways do private individuals come to shape the public? These questions are examined in the context of ICT-based media environments and in relation to three empirical studies: 1) OhmyNews - a global icon of citizen journalism - in which the ‘feminised' news produced by citizens (re- )contextualised private interests into public concerns, and allowed the public to make a real change in the 2002 Presidential election and the 2010 local elections; 2) online political satire, in which politics is situated in an entertainment mode through citizens' creative reinterpretation, and which helped mobilise citizens' political interest and action during the 2004 Presidential impeachment and general election; and 3) the politicisation of teen fandom, in which music fans were mobilised as political actors in the 2008 anti-US beef protest. The thesis employs a wide range of research methods including participant observation, interpretive textual analysis, and semi-structured and in-depth interviews. In this way the thesis identifies a complex linkage of traditionally separated spheres, such as reason and affect, news and entertainment media, and expert and common knowledge.