This work investigates how digital participation among young citizens in Southern Europe shapes their democratic attitudes and orientations. Building on recent debates on youth political engagement, it contrasts two perspectives: the democratic deficit thesis, which views online activism as a critical response to weak institutions, and the “bridging effect” thesis, which conceives digital spaces as arenas of civic socialization for previously disengaged youth. Using new comparative survey data from Portugal, Spain, and Italy, the study identifies distinct profiles of youth activism—“digital-only” activists, “full-spectrum” activists, and non-activists—and examines their impact on satisfaction with democracy, normative support for democratic institutions, and commitment to liberal democratic values. The quantitative cross-national analysis highlights the ambivalent role of digital activism: while it strengthens democratic attitudes compared to inaction, its horizontal and less institutionalized character also raises challenges for the consolidation of traditional liberal consensus.