The increasing importance of civil rights issues as a national policy priority during the 1950s and 1960s set in motion a series of events that ensured the transformation of the Democratic Party. The effect of inter-group tensions on the roll call voting decisions of members of the United States House of Representatives considering selected civil rights and unemployment policies between 1955 and 1980 are analyzed to determine the consequences of these pressures on the fate of the Democratic Party. Two alternatives to the development of the party are explored. One suggests that Democratic legislators responded to white majorities, becoming less likely to support national party agendas in areas with high levels of inter-group tensions. Responsiveness would transform the party by realigning ideologically divergent political coalitions. The second alternative suggests that Democrats did not respond to inter-group tensions, but rather adhered to party agendas and were displaced from office as a result of popular discontent. As a consequence of displacements the Democratic Party would become smaller but more ideologically centralized allowing the possibility of a truly national Democratic Party.

Following Tilly’s (2001) recommendations for the use of environmental variables a spatial unit of analysis is developed and employed to address the relationship between inter-group pressures and roll call voting decisions. Measuring inter-group tensions within spatial units provides an improvement over political or administrative units for estimating the areas of overlap of majority and minority group members, and provides a clearer estimate of the pressures potentially influencing legislative decisions. Patterns of Democratic gains and losses following the Civil Rights Movements and response to inter-group pressures indicate a move toward party nationalization. At the same time, one ideological divide remained intact. Northern and southern regions of the country remained divided on the extensions of political rights. This ideological divide, however, was confined to civil rights issues. Concerning unemployment policies, southern Democrats became more supportive, but northern Democrats responded to inter-group tensions—becoming less supportive. The results indicate a considerably more nationalized Democratic Party following the civil rights era, however, in a way that reduced the party’s ability to pursue core policies.