As opinion leaders and key participants emerge in social media, identifying influential users can help decision makers to effectively target the source of influence and hence bring about change in the communities. In this research, we developed an approach to identifying influential users in online social networks of interest to policy makers and the general public. We present findings from an empirical study of the U.S. immigration reform discussion, in which more than 300,000 users posted 909,035 tweets during May-November 2013. We present findings of our analysis, provide the lists of influential users identified, and discuss the implication on predictive analytics and social media analytics. This research should contribute to providing a new case and new empirical findings of applying influence analytics to analyzing social media networks, and has strong implications on predictive analytics, business intelligence, and social media analytics.