A randomized controlled trial was conducted to examine the impact of political mobilization messages on Facebook users during the 2010 US congressional elections. The study involved 61 million users and tested the effects of social messages, informational messages, and a control group. The results showed that social messages, which included cues from users' social networks, significantly influenced political self-expression, information seeking, and real-world voting behavior. The effect of social transmission on real-world voting was greater than the direct effect of the messages themselves, with strong ties (close friends) playing a key role in spreading behavior. The study found that users who received social messages were more likely to click the "I Voted" button and to seek information about polling places compared to those who received informational messages. Additionally, the effect of the messages on real-world voting was more pronounced when the messages were seen by close friends. The results suggest that online political mobilization can have a direct effect on political behavior and that messages including cues from an individual's social network are more effective than information-only appeals. The study also examined the indirect effects of the messages through social networks. It found that close friends had a significant influence on voting behavior, while ordinary friends had less impact. The results indicate that social influence is a key factor in behavior change, and that online networks can be effective in influencing real-world behavior through strong ties. The study highlights the importance of social networks in political mobilization and suggests that online social media can play a significant role in shaping political behavior. The findings have implications for understanding the role of online social media in society and for developing effective strategies for political mobilization.A randomized controlled trial was conducted to examine the impact of political mobilization messages on Facebook users during the 2010 US congressional elections. The study involved 61 million users and tested the effects of social messages, informational messages, and a control group. The results showed that social messages, which included cues from users' social networks, significantly influenced political self-expression, information seeking, and real-world voting behavior. The effect of social transmission on real-world voting was greater than the direct effect of the messages themselves, with strong ties (close friends) playing a key role in spreading behavior. The study found that users who received social messages were more likely to click the "I Voted" button and to seek information about polling places compared to those who received informational messages. Additionally, the effect of the messages on real-world voting was more pronounced when the messages were seen by close friends. The results suggest that online political mobilization can have a direct effect on political behavior and that messages including cues from an individual's social network are more effective than information-only appeals. The study also examined the indirect effects of the messages through social networks. It found that close friends had a significant influence on voting behavior, while ordinary friends had less impact. The results indicate that social influence is a key factor in behavior change, and that online networks can be effective in influencing real-world behavior through strong ties. The study highlights the importance of social networks in political mobilization and suggests that online social media can play a significant role in shaping political behavior. The findings have implications for understanding the role of online social media in society and for developing effective strategies for political mobilization.