Political Polarization and the Dynamics of Political Language: Evidence from 130 Years of Partisan Speech

We use the digitized Congressional Record and the Google Ngrams corpus to study the polarization of political discourse and the diffusion of political language since 1873. We statistically identify highly partisan phrases from the Congressional Record and then use these to impute partisanship and political polarization to the Google Books corpus between 1873 and 2000. We find that although political discourse expressed in books did become more polarized in the late 1990s, polarization remained low relative to the late 19th and much of the 20th century. We also find that polarization of discourse in books predicts legislative gridlock, but polarization of congressional language does not. Using a dynamic panel data set of phrases, we find that polarized phrases increase in frequency in Google Books before their use increases in congressional speech. Our evidence is consistent with an autonomous effect of elite discourse on congressional speech and legislative gridlock, but this effect is not large enough to drive the recent increase in congressional polarization.