What method allows interest groups and campaigns to raise contributions directly through mail?

The correct choice, direct mailing, refers to a method widely utilized by interest groups and campaigns to solicit contributions through the postal service. This strategy involves sending out fundraising letters, brochures, or other promotional materials directly to potential donors. It allows organizations to reach a large audience without the need for face-to-face interactions, making it a cost-effective way to raise funds.

Direct mailing has several advantages; it enables targeted outreach to individuals who have previously donated or expressed interest in specific issues, and it allows campaigns to communicate their messages directly to supporters. This method can help raise awareness and motivate constituents to contribute financially. It is particularly significant during election cycles when campaigns seek to mobilize resources quickly.

The other options represent different fundraising mechanisms or organizational structures that do not specifically focus on the direct appeal through the mail. For instance, Super PACs can raise unlimited funds but typically do so through coordinated efforts and events rather than direct mail campaigns. Similarly, 501 organizations refer to a type of non-profit that can engage in advocacy but are often limited in their political activity, while Leadership PACs are political action committees formed to support other candidates rather than their own fundraising through direct mail strategies.