Voting Behavior in the US House and Senate Regional Shifts and Contemporary Changes in Party Coalitions

If we want to know what is happening to political parties today, the answer depends in part on how we define the term `party' and in part on the time frame used for analysis. In this paper we focus on parties as voting coalitions in the US House and the Senate over the last 40 years. To assess the ideological placement and cohesiveness of each party in the House and Senate, we use adjusted scores issued by the Americans for Democratic Action (ADA). Our adjustment corrects for changes in the ADA's scale from year to year. The analysis is carried out by focusing on each of the four main regional factions comprising the parties. The cross-chamber comparisons for the Republicans show a high degree of stability with respect to ideological placement and cohesiveness; eastern Republicans maintain a more liberal stance throughout the period of analysis. For Democrats in both chambers there has been a liberal shift in recent years and an increase in cohesiveness overall; the southern Democrats are distinctively mo...