Final answer:
Interest groups aim to influence policy while political parties seek to win elections and govern. Interest groups advocate for specific policies, whereas political parties nominate and support candidates for office.
Step-by-step explanation:
Interest groups and political parties are easily confused because they both engage in political activities and aim to influence public policy, but they serve different functions in the political system. Interest groups are organizations of people with common interests that advocate for specific policies or changes, without seeking to control government through elections. In contrast, political parties are organizations that nominate candidates to compete in elections with the goal of controlling government and policy-making.
The most important role performed by an interest group is to influence public policy. Interest groups may support political parties, but their main goal is not to win elections but to sway decision-makers and public opinion in favor of their causes. They can employ various tactics such as lobbying, litigation, grassroots mobilization, and public campaigns.