Within 24 hours of the phone call, send the donor a letter of thanks confirming the amount pledged, and include a pre-addressed return envelope. Custom t-shirts are a great product to help raise funds for your political campaign. They give supporters something in exchange for their donation, and they help promote the cause to a wider audience. Create several different types of design, all brand-aligned to the rest of your campaign, and then find a company/provider to manufacture and ship them.