Interest groups influence legislative outcomes by advocating for specific policies and mobilizing constituencies to engage with lawmakers. They use various tactics, including lobbying, public campaigns, and funding political action committees (PACs) to gain access to decision-makers and shape policy discussions. By providing research, expertise, and resources, interest groups can effectively persuade legislators to support particular agendas. Their involvement is crucial in a representative democracy, as they help to amplify diverse perspectives and ensure that various interests are considered in the legislative process.