The Public Sphere in Private Spaces: Quantifying Political Computer-Mediated Communication in Personal Messaging

Personal messaging apps have become widespread platforms for online communication, yet their role in spreading information is still not well understood due to encryption and privacy concerns. Using SIREN (Supporting Interdisciplinary Research in Encrypted Networks), a new mobile-phone-based data collection approach, we gathered 88,606 messages from 349 American adults during the 2024 U.S. Presidential Election. We characterize personal messaging as private interpersonal channels where relationships, rather than algorithms, shape information flow and credibility assessment. The results show that while 67.3% of participants received political content, only 1.1% received links to misinformation websites, raising questions about assumptions that misinformation easily spreads to private channels. Political messaging has two main functions: personal discussions (51.6% of participants) and elite political communication (48.1%). Message sharing follows power-law patterns, where a small number of senders account for most of the content. These findings suggest personal messaging platforms are important spaces for political conversation while maintaining relatively high information quality. They also suggest that claims about widespread misinformation in private digital spaces may be overstated. While some empirical findings are similar to those of past work on the open web, other findings diverge, showing how these private interpersonal channels are similar and different as a platform for computer-mediated communication.