The use of mobile instant messaging services (MIMS) for the dissemination of electoral information has been increasing in recent years. Drawing on a novel dataset from a 2015 post-electoral survey in Spain, we focus on individuals’ digital political behavior, both public and private. Our results show that, in a context of high electoral volatility and polarization, right-wing supporters are willing to engage in political persuasion activities using tools such as MIMS in the private digital arena but not publicly (e.g., on social media). In contrast, left-wing milieus develop mobilization efforts in both public and private settings. We argue that distinct political styles are key in accounting for the difference in channels of partisan persuasion, in which preference falsification mechanisms are involved in the public sphere. These results bear important implications for the understanding of false information exchanges in the private sphere, social media activism, and political participation. Additionally, they help us shed light on the recurring failure of polls in capturing electoral behavior among right-wing voters in polarized elections and referenda.