Comparing the Influence of Social Networks Online and Offline on Decision Making: The U.S. Senate Case

Along with individuals’ ideological factors, various network properties play a crucial role in the process of legislators’ political decision-making. Social networks among legislators provide relational resources through which communication occurs, exerting social influence among the members in a network. This chapter examines six social relationships among the members of the 109th United States Senate as predictors of senatorial voting (roll call votes), (1) shared committees, (2) co-sponsorships, (3) party membership, (4) PAC donation, (5) geographical contiguity, and (6) internet hyperlinks, which may be considered as direct or indirect representations of communication networks. The six networks are modeled using MRQAP. Results suggest that roll call voting was predicted by party membership, co-sponsorship, geographical proximity, and PAC donation networks, while shared committee membership did not contribute significantly. As for hyperlinks, the result was mixed, showing a small variance of contribution in a simpler model but not significant with more complex models. Suggestions for future research are addressed.