Minneapolis-St. Paul-based 3M Corp. expects to face activists Tuesday, both inside and outside its annual shareholders meeting, because of its alleged secret spending on political campaigns.

A group of institutional investors, led by Trillium Asset Management Corp. of Boston, has introduced a shareholder proposal [PDF] asking that the corporation refrain from political spending, both directly and indirectly (i.e., funneling company money through third-party groups like so-called Super PACs).