501(c)(3) organizations are “absolutely prohibited” from engaging, either directly or indirectly, in political activity. This includes public statements in favor of or against any candidate for public office made on behalf of the organization. Violations of this rule can result in denial or revocation of 501(c)(3) status and excise taxes.
Nonprofit organizations have to be aware of the partisan actions of their employees and volunteers. Employees and volunteers can take public political positions, but they must do so on their own time, use their own resources, and make sure they are not leading others to believe that they speak for the nonprofit. In order for a nonprofit organization to ensure that these standards are met by its employees and volunteers, it is important for the organization to create and implement a policy addressing the dos and don’ts of a employees and volunteers engaging in political activity on their own time.
The IRS has resources that help 501(c)(3) organizations avoid illegal political activity. You might also wish to contact your trusted nonprofit adviser for help developing your organization’s political activity policy.