By Josh Zingher, Binghamton University

Cross-post from The Quantitative Peace and LSE
Originally Published March 27, 2014

Demographic changes mean that traditional Republican constituencies are shrinking as the Democrats grow. 

It is difficult to discuss electoral politics in the United States without talking in terms of social groups. Journalistic accounts of party competition often stress the important role that specific constituencies play (such as the “evangelical” or “Latino” vote) in determining the outcome of presidential elections. A great deal of political science research has shown that these social cleavages structure party competition. However, the political importance of these social cleavages can change, which can lead to a reshuffling of the social bases of the party coalitions. In addition, demographic changes have the potential to dramatically reshape the political landscape, as new groups enter the electorate and the ratio of existing groups changes. I am interested in how changes in the cleavage structure and in the ratio of groups work in conjunction to transform electoral coalitions. In new research, I investigated two related questions: what group memberships influence individual level voting behavior and how has the number of votes each political relevant group contributes to the party coalitions changed over time?

Identifying the Group Bases of Party Support
What groups are politically relevant? To answer this question, I conducted a multivariate statistical analysis utilizing nearly 60 years of American National Election Survey (ANES) spanning 1952 to 2008. I utilized group memberships as independent variables and vote choice as the dependent variable. The battery of group memberships included variables for class, race, ethnicity, region, education, birth cohort, and age. I define politically relevant group memberships as those that exert a statistically significant influence on individual level vote choice. I ran a separate regression for each decade, which allowed me to assess whether the effect of specific group memberships have changed over time. The substantive results of these models are displayed in Figure 1 below.

Figure 1: The Predicted Effect of Group Memberships on Vote Choice–First Differences (Click to view larger image.)

The results of the analysis displayed in Figure 1 demonstrate that the following group memberships lead individuals to be consistently and statistically significantly more likely to support one party over the other:

Table 1: The Core Democratic and Republican Social Groups

Democratic Groups

Republican Groups






Church Attendees












This analysis highlights the continuity and change that characterizes each parties’ social base. Some groups have been stable members of a party coalition for the last 60 years. African Americans, Catholics, union members, and Jews have all been consistent members of the Democratic coalition, while whites and Protestants have reliably favored the Republicans.

Yet, other groups’ political leanings have changed considerably. Whites in the Southern United States were once reliably Democratic voters; today, they are one of the most solidly Republican constituencies. The divide between the religiously devout and the secular has also become more politically important in recent elections. Non-religious voters have become increasingly likely to vote for Democratic candidates, while weekly church attendees have become more likely to support Republicans. Similarly, a partisan “gender gap” emerged in the 1980s. Men have become significantly more likely to vote for Republican candidates, while women have become more likely to support Democrats. In sum, many traditionally politically important social cleavages have endured (e.g., black/white), while other cleavages have become politically important only in recent decades (e.g., secular/religious or female/male).

Group Contributions and the Importance of Demographic Changes
The preceding analysis established what group memberships significantly influence vote choice. However, simply understanding which group memberships shape individual level voting behavior paints an incomplete picture of electoral change. Winning an election is not about having core groups of loyal supporters. Rather, parties must be able to obtain a majority of votes in order to win elections. Thus, any process that leads to a party gaining more or less from a specific social group is potentially politically consequential. Figures 2 and 3 show my calculations for each group’s contribution to the Democrats’ and Republicans’ party coalitions, measured as a proportion of the party’s total votes. There have been considerable changes in the size of group contributions to the party coalitions–many of which highlight the important role that demographic shifts play in reshaping the party coalitions.  

Figure 2: Group Contribution as a Proportion of Democrats’ Total Votes: 1952-2008
Figure 3: Group contribution as a Proportion of Republicans’ Total Votes: 1952-2008

The Democratic Party has been obtaining an increasing proportion of its support from groups that are growing as a proportion of the electorate, such as Latinos, college graduates and the non-religious. In addition, increasing turnout among Latino and African American voters has led to the size of these groups’ contributions to the Democratic coalition. The Republican Party is being forced to confront the opposite scenario–many Republican groups, whites, Protestants, and weekly church attendees are making up a continuously shrinking proportion of the electorate. Thus far, the Republican Party has been able to offset demographic changes via high turnout among their core groups as well as by winning an increasingly large majority of the Southern white vote.

What conclusions can be drawn from this analysis? Firstly, the group sources of party support are dynamic and the political relevance of certain social cleavages ebb and flow across decades, which is evidenced by the changing relationship between group membership and vote choice. Secondly, demographic changes can be politically consequential. The Republican Party is currently in the undesirable position of having to find new sources of electoral support in order to remain viable in future elections. The Republican Party’s need to find new sources of electoral support has come about, not as a result of the loss of electoral support among loyal groups–rather, the Republican Party must find new sources of electoral support simply because traditionally Republican constituencies are making up a shrinking proportion of the electorate.

This blog post is based on the paper, “An Analysis of the Changing Social Bases of America’s Political Parties: 1952-2008.”

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