Corporations are OWNED by people, & they have a right to petition their government.
 The spending of money on politics is the very essence of free speech, i.e. putting ones money where their mouth is.
Now IF a corp. is able to buy a politician, would not the way of protecting free speech, & dealing with that problem, be to eliminate as much as possible just what the Pol. has jurisdiction over.
Example, enacting a flat tax on all net revenue, with nothing more than a personnel deduction.
 That change in, & of it's self would severely limit the favors the Pol has to sell.
 Limiting the size, & scope of the federal government would also go a long way in limiting just what a Pol. could do for a donor.
24 days !