Key Takeaways
1. Elite Polarization Drives the Transformation of the American Electorate
Party has experienced a re-naissance in American politics: far from being irrelevant to contemporary politics, party is once again the driving factor behind political behavior.
A dramatic shift. The American electorate has undergone a profound transformation since the 1970s. Once characterized by ideologically diverse parties and high levels of split-ticket voting, today's political landscape sees partisanship and ideology much more tightly aligned. This resurgence of party as a central force in political behavior is a defining feature of contemporary American politics.
Elite-driven change. This massive shift is primarily explained by the increasing polarization of political elites. In the 1950s and 60s, both Democratic and Republican elites were ideologically heterogeneous, with significant overlap. However, by the 1990s and 2000s, elites became sharply polarized, with most Democrats on the left and most Republicans on the right. This elite-level divergence clarifies what it means to be a Democrat or a Republican.
Voters respond. As elites pull apart, they send clearer signals about their policy positions. Ordinary voters then use these increasingly distinct cues to align their own partisan and ideological beliefs. This process, termed "sorting," is the core mechanism explaining the tighter party-ideology link observed today, which in turn fuels the rise in party voting and influences how candidates engage with voters.
2. Voter Sorting Aligns Partisanship and Ideology
I refer to this alignment of partisanship and ideology as sorting; sorted Democrats are liberals, and sorted Republicans are conservatives.
Defining sorting. Sorting describes the process where voters align their partisan affiliation with their ideological outlook. In a sorted electorate, liberals predominantly identify as Democrats, and conservatives predominantly identify as Republicans. This creates a stronger correlation between an individual's party identification and their ideological self-placement.
Distinct from polarization. It's crucial to distinguish sorting from mass polarization. Sorting refers to the reorganization of voters within the existing ideological spectrum, making parties more internally homogeneous. Polarization, on the other hand, implies that voters are adopting more extreme ideological positions, moving away from the center. While sorting can lead to a modest increase in polarization, the two are distinct phenomena.
Two pathways to sorting. When an individual voter transitions from unsorted to sorted, they can do so in one of two ways:
- Party-driven sorting: Adjusting their ideology to fit their existing partisanship (e.g., a liberal Republican becomes a conservative Republican).
- Ideology-driven sorting: Changing their partisanship to align with their existing ideology (e.g., a liberal Republican becomes a liberal Democrat).
The book explores which of these pathways is more prevalent in the American electorate.
3. Clearer Elite Cues Facilitate Mass Sorting
Elite polarization, by clarifying where the parties stand on the issues of the day, causes ordinary voters to sort.
The causal mechanism. Elite polarization clarifies party positions through two main mechanisms. First, it increases the ideological distance between the parties, making Democratic and Republican stances on issues more distinct. Second, it makes each party more ideologically homogeneous, reducing internal dissent and presenting a unified front. These clearer, more consistent signals simplify the cue-taking process for voters.
Sources of elite cues. Voters learn about these elite positions from various sources. Presidential candidates and members of Congress are key actors, defining "the party's" stance. Information is disseminated through:
- Intensive election campaigns and candidate advertising.
- Strategic communication by politicians highlighting their party's strengths.
- Informal activists who transmit elite messages to less engaged voters.
- Interest groups and social movements aligning with specific parties, particularly on controversial social issues.
- "Accidental data" encountered in daily life, like news headlines or commercials.
Media's amplifying role. Changes in the media environment, such as increased media choice and narrowcasting, further contribute to clearer cues. The proliferation of partisan news outlets and selective exposure patterns create "echo chambers" where voters are inundated with messages reinforcing their side's positions, heightening awareness of party stances and accelerating sorting. However, the impact of these media changes is complex and may be limited for many Americans who consume less partisan mainstream news.
4. Sorting is Widespread but Leads to Modest Mass Polarization
While there has been a large increase in voter sorting, the corresponding increase in voter polarization is quite limited.
Empirical evidence of sorting. Analysis of National Election Study (NES) data confirms a significant increase in voter sorting across a range of issues since the 1970s. Voters are increasingly able to correctly place Democrats to the left of Republicans on ideological and policy scales, and a larger percentage of the electorate aligns their own positions with their party's elites. This trend is observed on issues from economic policy and defense spending to abortion and aid to minorities.
National phenomenon. Sorting is not confined to specific regions or groups. While the South's realignment played a role, sorting is a widespread national phenomenon, with both northern and southern voters showing increased alignment. It's also driven by both:
- Conversion effects: Existing voters adjusting their beliefs.
- Replacement effects: Younger, already-sorted cohorts entering the electorate.
Even the rise of evangelical Christians in the Republican Party, while contributing to sorting on social issues like abortion, is complemented by broader cue-taking among all Republicans.
Limited mass polarization. Despite considerable sorting, the increase in mass polarization (voters adopting more extreme ideological positions) has been modest. While there are fewer moderates, the electorate has not become deeply bimodal, and the number of "extremists" has not significantly increased. Sorting primarily causes voters to "choose a side" (e.g., move from moderate to slightly liberal) rather than moving to the ideological poles. This means that while the distribution of ideology within each party has shifted, the aggregate distribution of ideology in the electorate has changed only slightly.
5. Voters Primarily Sort by Adjusting Ideology to Fit Partisanship
I find that voters typically shift their ideology to fit with their party identification; ideology-driven party exit (changing one’s party to fit with one’s ideology) occurs in only a narrow set of circumstances.
Party as the "unmoved mover." When an unsorted voter decides to align their beliefs, the dominant pathway is party-driven sorting. This means voters are more likely to adjust their ideological positions to match their existing party identification rather than changing their party affiliation to fit their ideology. This aligns with decades of political behavior research emphasizing partisanship as a stable, long-term force shaping political attitudes.
Ideology's malleability. Unlike the stability of party identification, ideology is often more malleable for most voters. Many citizens do not possess deeply coherent or stable ideological belief systems, making them more susceptible to adopting elite cues that align with their party. Party identification acts as a powerful "perceptual screen," influencing how individuals interpret political information and form issue positions.
Exceptions to the rule. Ideology-driven sorting, where voters change their party to match their ideology, is less common and typically occurs under specific conditions:
- Among highly politically sophisticated respondents who possess coherent, stable ideological beliefs.
- During periods of significant elite realignment, such as the mid-20th century southern realignment, where conservative Democrats abandoned the party as it moved left on civil rights and social welfare.
However, even for highly educated voters, party-driven sorting remains the more prevalent path, suggesting the enduring power of party identification.
6. Sorting Increases Party Loyalty and Affective Polarization
After sorting, voters’ affective evaluations of the parties are 19 points more polarized (on a 100-point scale).
Enhanced party loyalty. Sorting profoundly impacts individual voter behavior. When voters move from being unsorted to sorted, their cross-pressures diminish, making their decision calculus simpler. Sorted voters become significantly more likely to support their same-party presidential nominee and less likely to split their ticket, demonstrating increased loyalty to their party at the ballot box.
Affective polarization. Beyond voting behavior, sorting also intensifies how voters feel about political parties and candidates. Sorted voters evaluate their own party more positively and the opposing party more negatively. This "affective polarization" means they feel warmer towards their own party and cooler towards the opposition, creating a stronger emotional attachment to their political "team." This effect extends to evaluations of presidential and vice-presidential nominees.
Increased attitude consistency. Sorting also drives greater attitude consistency among voters. When a voter sorts on one issue (e.g., aligning their tax policy views with their party), they become more likely to adopt their party's positions on a range of other issues (e.g., abortion, affirmative action, defense spending). This leads to more consistently liberal or conservative clusters of attitudes within the mass parties, making them more ideologically homogeneous.
7. A Sorted Electorate Shifts Campaign Strategies Towards Base Mobilization
Sorting partially accounts for this shift in campaign strategy. As more voters are sorted, the size of each party’s base increases.
From swing to base. For decades, the conventional wisdom in American elections was to appeal to the political center and convert undecided "swing" voters. However, starting in the 1990s, campaigns began a significant shift towards a "base mobilization" strategy, focusing resources on ensuring the party faithful turn out. This was notably evident in the 2004 election, where both parties heavily invested in mobilizing their core supporters.
Sorting enables new strategies. Sorting provides a partial explanation for this strategic shift. As more voters become sorted, the size of each party's committed base increases. This makes base mobilization a potentially more lucrative source of votes compared to the diminishing pool of truly undecided swing voters. While campaigns still court swing voters, a well-sorted electorate makes a base-focused strategy more viable and attractive.
Implications for targeting. This shift also highlights the growing importance of targeted appeals. Messages designed to motivate core partisans and sorted voters are distinct from those aimed at swing voters. The ability to precisely target these different groups allows campaigns to tailor their rhetoric, reinforcing the loyalty of the sorted while still attempting to persuade the undecided. This balance between base and centrist appeals may represent an informal equilibrium in the current political environment.
8. Voter Sorting Sustains Elite Polarization Through Feedback Loops
So while sorting is elite driven, a better-sorted electorate also has important consequences for elite behavior.
The feedback loop. While elite polarization initially causes voter sorting, a sorted electorate can, in turn, help sustain elite polarization. As voters become better sorted, the ideological distribution within each mass party becomes more homogeneous. This increased homogeneity in the mass parties, particularly within primary electorates, creates new pressures on political elites.
Pressure on candidates. More homogeneous primary electorates make it challenging for candidates to moderate their positions and move towards the ideological center without risking a primary challenge from more extreme opponents. Politicians who appear too soft or bipartisan may be vulnerable to challengers who align more closely with the "purist" wing of their party. This dynamic incentivizes candidates to maintain noncentrist positions, thereby perpetuating elite polarization.
Broader consequences. This feedback loop has broader implications for congressional politics. The decline in moderate legislators, partly sustained by sorted electorates, can reduce the capacity for compromise and lead to increased partisan bickering. It may also influence the types of leaders selected by congressional parties, favoring those who can effectively mobilize a cohesive, ideologically aligned base. Thus, sorting, once initiated by elites, becomes a factor in maintaining the very elite polarization that created it.
9. Sorting Presents a Fundamental Dilemma for Democratic Citizenship
If what we want is more people to enthusiastically cheer for their side, and to have some way of translating their underlying preferences into votes, then sorting is unquestionably a positive development.
Normative benefits. From one perspective, sorting is normatively desirable for democratic citizenship. It helps voters make "correct" decisions by aligning their underlying values with their vote choices, strengthening the connection between the public and government policies. Sorted voters are more engaged, more consistent in their attitudes, and more likely to participate meaningfully in the democratic process, fulfilling the ideal of "responsible parties" that offer clear programmatic choices.
Potential harms. However, sorting also carries potential risks. It can "balkanize" the electorate, leading to increased affective polarization where voters view the opposing party not just as different, but as "the bad guys." This heightened partisan spirit, while fueling engagement, can make politics more passionate and less amenable to compromise and negotiation. It risks creating an environment where emotional responses overshadow rational deliberation.
An impossible standard. This highlights a fundamental tension in the standards for "good citizens." We often encourage active, enthusiastic participation while simultaneously expecting citizens to set aside partisan convictions and think independently. Sorting demonstrates that meaningful participation often goes hand-in-hand with increased partisanship. If citizens rely on parties to make sense of the political world, then a more participatory politics may inevitably be a more partisan politics, challenging traditional ideals of independent citizenship.
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