"We demonstrate that personal connections amongst politicians have a significant impact on the voting behavior of U.S. politicians. Networks based on alumni connections between politicians, as well as common seat locations on the chamber floor, are consistent predictors of voting behavior. For the former, we estimate sharp measures that control for common characteristics of the network, as well as heterogeneous impacts of a common network characteristic across votes. For common seat locations, we identify a set of plausibly exogenously assigned seats (Freshman Senators), and find a strong impact of seat location networks on voting. We find that the effect of alumni networks is close to 60% of the size of the effect of state-level considerations. The network effects we identify are stronger for more tightly linked networks, and at times when votes are most valuable"--National Bureau of Economic Research web site.