Tax-exempt organizations cannot endorse candidates, host partisan events, use resources for campaigns, or display political signs. Violations risk the loss of tax-exempt status.
To report violations, use IRS Form 13909 (see link below). Complete it with details of the organization and violation, and submit by mail, fax, or email. Mail to 1100 Commerce Street, Dallas, TX 75242-1198, fax (214) 413-5415, or email eoclass@irs.gov. You should also report it to the FEC