Social media offers new opportunities for politicians to mobilize and persuade a large pool of potential supporters, but also allows voters to select whose messages they get directly exposed to. Knowing the factors that make individuals more likely to follow particular politicians may help understand the communication strategies of politicians and also the effects of social media on political polarization. However, information about the offline attributes of individuals in social media is not directly observable. Using a unique database with survey data about the sociodemographic characteristics and political attitudes of 5,580 Twitter users, we show that voters exposed to messages from the Members of Congress are more politically motivated and ideologically extreme than the rest of the Twitter users and that ideological distance between the user and the politician plays a major role in determining following behavior. Our results provide a direct validation of previously hypothesized behavior in the literature and have implications for the discussion about how tools that enable both general and microtargeted communication with voters contribute to a fragmented political debate on the Internet.

This paper describes an approach to large-scale modeling of sentiment analysis for the social sciences. The goal is to model relations between nation states through so-cial media. Many cross-disciplinary appli-cations of NLP involve making predictions (such as predicting political elections), but this paper instead focuses on a model that is applicable to broader analysis. Do cit-izens express opinions in line with their home country’s formal relations? When opinions diverge over time, what is the cause and can social media serve to de-tect these changes? We describe several learning algorithms to study how the pop-ulace of a country discusses foreign na-tions on Twitter, ranging from state-of-the-art contextual sentiment analysis to some required practical learners that filter irrel-evant tweets. We evaluate on standard sentiment evaluations, but we also show strong correlations with two public opin-ion polls and current international alliance relationships. We conclude with some po-litical science use cases. 1