Understanding the Connection Between Party Affiliation, Partisanship, and Political Beliefs in the United States

Gregory A. Huber
Ebonya Washington
Fieldwork by:
Connecticut, United States of America
2008 - 2008
Target group:
  • Voters
Outcome of interest:
  • Electoral participation
Intervention type:
  • Information

Affiliation with political parties may strongly affect attitudes and behavior. Researchers from Yale University conducted an experiment examining the effects of political party identification on political attitudes and opinions. Participants in the study who received a printed letter indicating that they must register with a political party to vote in an upcoming election were more likely to affiliate with a party, change their views on political issues, and change their voting behavior. These results imply that group associations alone may influence individuals’ behaviors and attitudes.

Policy issue

Political parties are an important part of the political process in many countries. Research from a variety of disciplines suggests that being affiliated with a political party may powerfully affect attitudes and behavior. There is a strong correlation between belonging to a political party and political opinions, preferences for biased political information, and the persistence over time of party affiliations. Individuals who perceive themselves as members of a political party may internalize the group' s norms or values and use these as a guide for their own attitudes and behaviors. As a result, influencing people to join political parties may affect individual voting behavior and election outcomes. However, existing research has not demonstrated that these relationships are causal or whether or not affiliations alone significantly affect political outcomes.

Context of the evaluation

In 2008, the Unites States held an election to select the next president. As the first step in this process, the major political parties hold primary contests which they use to select the candidate they want to nominate for the general presidential election. Although all registered voters may vote in any general presidential election, voters in states with "closed primaries" are only permitted to participate in primary contests of their registered political party.

Connecticut is one state that operates a closed primary." In order to participate in the primary, voters must be registered with a specific political party, such as Democrat or Republican. Those registered as independents are barred from voting unless they choose to register with a specific party prior to the election.

Details of the intervention

Researchers from Yale University examined the effects of partisanship (i.e., being associated with either the Democratic or Republican Party) on voter attitudes. Researchers designed an intervention that encouraged party affiliation and then examined the effect of registering with a party on attitudes and voter behavior. The study took place in three phases:

  • In January 2008, researchers conducted a telephone survey of registered voters who were not registered with a party to measure political opinions including which party the respondents felt closer to (Those who declined to identify with the Democratic or Republic Party but stated they felt closer to one of the parties overall were classified as "Latent" Democrats or Republicans).

  • Fifty percent of those surveyed were randomly selected to receive a letter reminding the recipient of the upcoming election and explaining the need to affiliate with a party in order to vote. The treatment letter provided information about the potential benefit of party affiliation made it easier to change one' s registration.

  • Four months after sending the letters, researchers followed up with a phone survey about respondents' partisanship and other attitudes.

The goals of the evaluation were to test the effect of randomly strengthened partisan identities on political attitudes and opinions.

Results and policy lessons

Impact on Party Identification: In a follow up survey, the latent Democrats or Republicans who received the letter were 8.1 percentage points more likely to identify with their previous latent party than those in the control group.

Impact on Party Registration and Voter Turnout: The mailing also increased rates of formal party registration and participation in the 2008 primary election. For latent Democrats and Republicans, those who received the letter were 8.1 and 9.0 percentage points more likely to formally register with their latent party, respectively. This is a large effect compared to the 9.7 percent of latent Democrats and 2.8 percent of latent Republicans who registered with their party in the control group. In addition, the letter increased turnout in the primary by 4.6 percentage points, similar to the effect of door-to-door canvassing which can increase voter turnout by 5 to 10 percentage points.

The letter made it easier for those who wanted to exercise their right to vote in a primary to affiliate with a political party and vote. In fact, receiving the letter caused a substantial increase in self-reported party identification and an increase in partisan leaning views. The results support the theory that registering with a party induces individuals to evaluate members of their group more favorably than members of opposing (party) groups. There are many situations in a typical person’s daily life where the state or other organizations ask the individual to designate or affirm a group identity and these results suggest that these procedures themselves might affect people’s attitudes.

Gerber, Alan S., Gregory A. Huber, and Ebonya Washington. 2010. "Party Affiliation, Partisanship, and Political Beliefs: A Field Experiment." The American Political Science Review 104 (4): 720-744.