It just doesn't wash that the senate didn't know the law when they registered as a 501(c)3 organization. The Form 990 they should file each year has several questionnaire sections where they must answer whether they influenced or attempted to influence legislation. In addition, a university should have knowledgable advisors, either lawyers or CPA's that
should know the specifics of the law.
They just figured they are above the law, and if past trends continue, they would get away with it anyway, just like all other liberal subversive 501(c)3's have.