Interest groups influence public policy through various strategies including lobbying, research funding, and grassroots campaigns. By mobilizing citizens and leveraging financial resources, they aim to sway lawmakers and public opinion on specific issues. These groups often provide information and expertise to policymakers, which can shape legislation in their favor. However, this influence raises concerns about disproportionate power wielded by well-funded interests over the democratic process, making it crucial for citizens and legislators to be aware of potential biases in decision-making.