What are the primary factions within the Democratic and Republican parties, and to what extent do rival factions cooperate? We address these questions using a unique data set of information sharing between party organizations, media outlets, 527s, and interest groups. Using social network methods, we identify two major information-sharing clusters, or expanded party networks; these networks correspond to a liberal/Democratic grouping and a conservative/Republican grouping. We further identify factions within each party network, but we find a high degree of cooperation between party factions. That is, our data suggest that beneath the intraparty disagreements we observe in primary elections and policy debates there is a subterranean pattern of organizational cooperation.