After Citizens United Bernie Sanders proposed the Saving American Democracy Amendment
http://www.change.org/petitions/the-saving-american-democracy-amendmentIt is a liberal wet dream but I can't see that ever passing unless there were some kind of massive event of corporate corruption ala Teapot Dome level or bigger
BTW 'Personhood' amendment usually applies to banning abortion by redefining personhood to fetuses. That has been proposed at the state level in a few states and always failed. There has also been failed attempts at the federal level,
http://en.wikipedia.org/wiki/Human_Life_AmendmentI can't imagine that ever passing