“Social sorting” is a concept used by Mason (2016) to explain the process by which individuals’ social identities grow increasingly aligned with a partisan identity, reducing social cross‐pressures on political behavior. Roccas and Brewer (2002) have found that individuals who feel fewer cross‐pressures more strongly identify with their ingroups and are less tolerant of outgroups. Accordingly, we create “objective” and “subjective” measures of social sorting to help identify the mechanism by which individual partisans connect social sorting to partisanship in the CCES and a nonprobability Internet sample. As racial, religious, and ideological identities have cumulatively moved into greater alignment with Democratic and Republican identities in recent decades, American partisans have grown increasingly identified with their parties due to the psychological effects of identity alignment captured in objective and subjective sorting mechanisms. However, we find that this effect is more powerful among Republicans than among Democrats, due to the general social homogeneity of the Republican party. Contrary to the assessments of modern political punditry, Republicans are more susceptible to identity‐based politics.