Theories of pluralist democracy emphasize the importance of political groups, what Madison referred to as factions, in enhancing representation and helping people get what they want from the political system. Two key kinds of groups in American politics are political parties, which organize in order to seek control of government, and interest groups, whose goal is to influence government decisions.

Political parties link voters and elected officials, overcome government fragmentation, and help provide, through the promotion of partisanship, a coherent ideological opposition to the party in power. Parties have three components. The official party structure, or party organization, gets people elected to office through the process of electioneering, which includes, among other steps, the formal nominating conventions. The officials, once elected, form the party-in-government, whose job includes governing. The party-in-the-electorate encompasses all the people whose party identification ties them to the party, including the most active and loyal members, who form the party base. These three components come together in the responsible party model —an ideal model of how parties can provide an essential linkage in democratic politics.

The history of parties in the United States has evolved from an age of party machines, where party bosses controlled candidates and officeholders, partly through the practice of patronage. Reforms, including the introduction of party primaries, made the old machines obsolete by making the parties more democratic. Periods when one party has majority control of most elements of government are called party eras, signaled by a critical election and in existence until citizens switch their allegiance to another party through a political realignment. Dealignment takes place if voters change their party identification to identify as independents instead. The parties stand for different ideologies and policies, as can be seen in their party platforms. The preferences of their bases, or party activists, make them more different, while the need to win moderate voters in national campaigns pushes them back to the middle.

Interest groups can enhance democracy by increasing citizens’ opportunities for representation and participation; by educating policymakers; by assisting in building agendas; by providing program alternatives; and by monitoring programs. But many groups, especially when their goals involve the provision of collective goods accessible to all, have difficulty getting members to join and contribute to their efforts because of the free rider problem. They try to combat this problem by offering selective incentives: material, solidarity, or expressive benefits. Interest groups take several forms. Depending on the type of representation they are seeking to enhance and the kind of goals they pursue, they can be economic interest groups, equal opportunity interest groups, public interest groups, or government interest groups.

Interest groups seek to influence policymakers through an activity called lobbying. Lobbyists, many of whom work for the government at one time in a practice called the revolving door, may engage in direct lobbying, targeting Congress—through a variety of strategies including contributions to political action committees—the president, the bureaucracy, and the Courts. Indirect lobbying involves influencing the public to pressure lawmakers to do what the groups want. Techniques include the use of issue advocacy ads and social protest. When such lobbying by the public is spontaneous, we call it grassroots lobbying. When it is manipulated by corporate or organized interests it is called astroturf lobbying. Interest groups’ success at getting what they want can depend on their access to resources—primarily money, leadership, members, and information.