The 2010 elections were the most polarized in the electorate and in Congress since 1952. The sharp partisan divide has implications for the arguments in this book, especially for candidate-driven differences in ideological proximity to voters and electorates, and in valence differences. As an approximation, the incumbency effect in House elections is greatest when electoral polarization was lowest in the late 1970s and early 1980s. It is reasonable to expect that the 2010 elections were not amenable to valence effects, so if we find these effects we can be more confident of their power in less polarized political contexts.