Political Parties in the American Political System
Political parties are organizations that nominate candidates, run campaigns, and try to win control of government. They're central to how American democracy actually works, from who appears on your ballot to what laws get passed. Understanding how parties function and how they've changed over time is a big part of this unit.
Functions of Political Parties
Parties do a lot more than just pick candidates. Here are their core functions:
- Nominate candidates for office through primary elections or caucuses, giving voters a narrower set of choices in the general election
- Mobilize voters by organizing rallies, canvassing neighborhoods, and running get-out-the-vote efforts
- Coordinate campaigns by raising funds, developing strategy, and creating advertisements
- Facilitate collective action among officeholders who share the party label, so legislators can work together to advance a shared agenda
- Inform the public about political issues and the party's positions through platforms, debates, and media appearances
- Organize the government when the party wins a majority in the legislature or controls the executive branch, setting the policy agenda
- Build coalitions by reaching out to different groups of voters to broaden their support base
The key idea: parties are the main vehicle for translating what voters want into actual government action.
Political Parties vs. Interest Groups
These two get confused a lot, but they play different roles.
Both aim to influence public policy. The differences come down to scope, strategy, and structure:
- Scope of issues: Parties take positions across a wide range of topics (economic policy, social issues, foreign policy). Interest groups typically focus on a narrow set of issues or even a single one, like environmental protection or gun rights.
- Running candidates: Parties nominate and support candidates for office. Interest groups don't run their own candidates, though they may endorse or oppose candidates based on how well those candidates align with the group's goals.
- Structure: Parties have a formal hierarchy (national committee, state parties, registered voters). Interest groups have a more fluid membership united by a shared concern (donors, activists, advocates).
- Control of government: When a party's candidates win, that party can directly control government. Interest groups can only influence government indirectly through lobbying and public pressure.

Evolution of U.S. Political Parties
The U.S. party system has gone through several distinct eras. Each shift happened because major events or social changes caused large groups of voters to switch their loyalties. This process is called party realignment.
- First Party System (1792–1824): Federalists (strong central government, national bank) vs. Democratic-Republicans (states' rights, limited federal government)
- Second Party System (1828–1854): Democrats (states' rights, opposed national bank) vs. Whigs (strong federal government, economic modernization)
- Third Party System (1854–1890s): Republicans (opposed slavery expansion, economic modernization) vs. Democrats (divided over slavery, became the party of the South after the Civil War)
- Fourth Party System (1896–1932): Republicans (business interests, progressive reforms) vs. Democrats (farmers, laborers)
- Fifth Party System (1933–1968): Democrats (New Deal coalition, liberal policies) vs. Republicans (initially opposed the New Deal, gradually embraced conservative policies)
- Sixth Party System (1968–present): Democrats (social liberalism, progressive policies) vs. Republicans (social conservatism, free-market economics), with increasing polarization on social, economic, and political issues
The Evolution of the Two-Party System

Realigning Elections
Certain elections mark turning points where the party system fundamentally shifted. These are called realigning elections or critical elections:
- 1800: Thomas Jefferson's victory marked the rise of the Democratic-Republicans and the decline of the Federalists
- 1828: Andrew Jackson's victory brought a new coalition of common voters into the Democratic Party, solidifying the Second Party System
- 1860: Abraham Lincoln's election led to Republican dominance and triggered the Civil War
- 1896: William McKinley's victory cemented Republican strength among business and industrial interests
- 1932: Franklin D. Roosevelt's landslide built the New Deal coalition (labor, minorities, the South, urban voters), shaping the Fifth Party System
- 1968: Richard Nixon's victory and the Southern Strategy pulled white Southern voters toward the Republican Party, beginning the Sixth Party System
Why the Two-Party System Endures
The U.S. has had two dominant parties for almost its entire history. That's not an accident. Several structural factors reinforce it:
- Duverger's Law: The U.S. uses single-member districts with plurality voting (whoever gets the most votes wins). This system naturally favors two major parties because third-party candidates tend to split the vote without winning seats.
- Institutional barriers: Ballot access laws make it hard for third parties to even appear on ballots in many states. Campaign finance regulations also tend to favor the two major parties.
- Third-party influence: Even though third parties rarely win, they can still shape politics. The Progressive Party in 1912 (Theodore Roosevelt) pushed social and political reforms into the mainstream. Ross Perot's Reform Party in 1992 put fiscal responsibility and deficit reduction on the national agenda.
The bottom line: the electoral system itself reinforces two-party dominance, making it very difficult for a third party to break through.
Party Dynamics and Voter Behavior
Three concepts tie together how parties operate and how voters relate to them:
- Party identification is the psychological attachment a voter feels toward a particular party. It's shaped by family, social groups, and personal experiences, and it tends to be stable over time. This is one of the strongest predictors of how someone will vote.
- Party ideology refers to the core beliefs and values that guide a party's policy positions. For example, Democrats generally lean toward government intervention in the economy, while Republicans generally favor free-market approaches.
- Party polarization describes the growing ideological distance between the two major parties. As Democrats have moved further left and Republicans further right on many issues, the overlap between the parties has shrunk. This contributes to partisan conflict and legislative gridlock.