The fates of challengers in U.S. house elections: The role of extended party networks in supporting candidates and shaping electoral outcomes

Extended party network (EPN) theory characterizes political parties in the United States as dynamic networks of interest groups that collaboratively support favored candidates for office. Electoral predictions derived from EPN theory have yet to be tested on a large sample of races. We operationalize EPNs in the context of organized interest contributions to U.S. House campaigns. We deduce that support by a partisan community of interests signals the ideological credibility and appeal of a candidate. EPN integration overcomes voter ambiguity surrounding challengers' ideological preferences, and resources provided by these coordinating interest groups promote a consistent message about the candidate. Using data from the 1994-2010 cycles, we apply network analysis to detect EPN support of challengers and find that EPN integration substantially improves the electoral prospects of challengers. The effect of EPN integration is distinct from that of campaign resources. The findings provide support for EPN theory, as applied to congressional elections.