Achen and Bartels maintain that social identities and group associations are more influential factors in determining why voters switch allegiance between parties than policy-based reasoning. The authors acknowledge that there are many factors upon which voters’ decisions are based—such as economic conditions and candidates—but claim that one of the greatest forces driving democratic politics is voters’ connection to social groups. Since parties are the most publicly identifiable and politically influential groups within democratic societies, these connections assist in explaining both the durability of party affiliation and changes over time in partisan loyalty.

Achen and Bartels challenge the assumption that party affiliation is fundamentally based upon ideology. Although party leaders, activists, journalists, etc., frequently articulate ideologies when discussing parties, Achen and Bartels assert that ordinary voters tend to connect with parties via membership in social groups or inheritance of party loyalty rather than through clear policy objectives. Further, the authors indicate that partisanship tends to persist from generation to generation and can sometimes exist independently of policy preferences. To illustrate how identity influences partisan change, Achen and Bartels analyze three significant American realignments.

The first example cited is ethnic politics during the New Deal period. Specifically drawing on Gerald Gamm’s work regarding Boston, Achen and Bartels demonstrate that Jewish people, Irish Catholics, Italian Americans, African Americans, and Americans from the Northern states reacted differently to similar national political occurrences. Similarities in reaction patterns are difficult to attribute to a single ideological explanation of the New Deal. However, differences in reaction patterns become understandable once ethnic and religious identifications are considered to have a direct impact on political decision-making.

Next, the authors analyze John F. Kennedy’s candidacy for US president in 1960. The authors assert that voter responses to Kennedy’s campaign were significantly determined by voters’ religious identity. Specifically Catholic/Protestant identity determined voter response to Kennedy’s campaign in ways that clearly defined partisanship in measurable terms.

Achen and Bartels address the realignment of white Southern Democrats to the Republican Party following the civil rights era. The authors argue that white Southerner’s transition away from the Democratic Party cannot solely be explained by differing policy stances on racial issues. Rather, white Southern identity was instrumental in defining both initial Democratic Party loyalty as well as subsequent defection to the Republican Party. Achen and Bartels also explore abortion politics, demonstrating that when party coalitions shifted relative to abortion-related policies, voters tended to adjust both their party affiliation and issue-specific attitudes in ways consistent with their social identity.

The authors conclude that people generally vote for parties because of who they are rather than what they think. Furthermore, voters often allow parties to define what they think.

Achen and Bartels argue that party identification is perhaps the most dominant political identity in democratic society because it forms not just voting behavior, but also how citizens evaluate issues, facts, and the larger political environment. For many voters, party loyalty forms an immediate lens through which to comprehend political opponents as allies/enemies, and helps to develop rationales for their views. Achen and Bartels further assert that this process often appears as independent reasoning although it is likely mostly rationalization.

Achen and Bartels focus on partisan distortion of perceived positions held by parties on public policies. Utilizing survey data pertaining to government spending/services, the authors demonstrate that both Democratic respondents and Republican respondents had identical placements on an issue, yet viewed their respective parties as substantially closer to their positions than did respondents affiliated with the opposition party. This finding supports the notion that many voters do not begin with specific policy positions and subsequently elect the closest party position—rather, party identification often determines how close they perceive the parties’ positions to be.

Next Achen and Bartels review possible explanations using psychological and rational choice frameworks for how partisan distortion occurs. They claim that, either way, the results raise serious concerns about incorrect perceptions of reality.

Achen and Bartels generalize their analysis from issues to facts. The authors argue that many citizens create factual beliefs from combinations of partisan loyalty, folk wisdom, and limited information. By providing illustrations, such as beliefs relating to inflation, the Iraq War, and the federal budget deficit under President Bill Clinton, the authors demonstrate that the level of partisan affiliation greatly influences judgements even regarding objectively verifiable aspects of the political condition. The problem is not merely lack of information: Moderate levels of informational sophistication may make partisans particularly susceptible to making inferences based on partisan association, since they know sufficient information to realize the partisan implications of a fact without having actual knowledge of the fact.

Finally Achen and Bartels examine broader impacts resulting from partisan shifts brought about by the Watergate scandal. Using panel data collected in the 1970s, the authors demonstrate that responses to Watergate affected not only attitudes toward Nixon but also subsequent assessments of party proximity on unrelated issues (e.g., school busing, crime, government employment). The authors found these impacts were particularly prevalent among well-educated citizens. The authors conclude that higher levels of cognitive sophistication often reinforce partisanship rather than democratic responsiveness, causing citizens to reside in a “pseudo-environment” wherein group affiliation determines attitudes, policy preferences, and beliefs.