Interest groups shape political decision-making by influencing legislators and public policy through advocacy, lobbying, and campaigns. They represent specific interests, such as business, labor, or environmental concerns, and aim to sway decisions that align with their objectives. By mobilizing members, conducting research, and funding campaigns, these groups can effectively communicate their positions to policymakers. However, there are concerns about the disproportionate power some groups wield, which can lead to inequality in political influence and potentially skew the democratic process. Balancing interest group influence is vital for maintaining a fair political landscape.