Potential political campaign intervention by 501(c)(3)’s is the topic of this IRS FAQ.
Can an organization post information on its website (or link to other websites) about a candidate for public office?
A website is a form of communication. If an organization posts something on its website that favors or opposes a candidate for public office it is prohibited political activity. It is the same as if the organization distributed printed material, or made oral statements or broadcasts that favored or opposed a candidate.
If an organization establishes a link to another website, it is responsible for the consequences of establishing and maintaining that link even if the organization does not have control over the content of the linked site. Because the linked content may change, the organization should monitor the linked content and adjust or remove any links that could result in prohibited political activity.