Interest groups influence public policy by advocating for specific issues and interests. They engage in lobbying to persuade lawmakers, conduct research to support their positions, and mobilize public opinion. By providing information, expertise, and resources, interest groups can shape legislation, regulatory decisions, and political priorities. They often fund campaigns to support sympathetic candidates or use grassroots campaigns to raise awareness and pressure policymakers. The effectiveness of interest groups varies but they play a significant role in the political process, contributing to the formulation of laws that reflect their goals.