Many advocates of reform don't seem to realize that restrictions on corporate political expenditures have applied, and, pursuant to the proposed constitutional amendment would apply to their favorite not for profit advocacy groups, as well as "big bad" business corporations...
The insistence that "corporations aren't people" is employed selectively: The 4th and 5th amendments explicitly apply to "people" and "persons," but I have yet to hear any liberal advocate of campaign finance reform argue that the government may subject corporations to unreasonable searches and seizures or prosecutions devoid of due process...