I think you're radically mistaken on how corporate contributions work.

Near as I can find, corporations don't have carte blanche to give unlimited money to an individual campaign. In fact, corporations cannot give any money to an individual candidate's campaign.

Corporations can give money to Political Action Committees, but are limited by amount to the same as real people.

Corporations can give money to SuperPACs, but so can real people.

http://www.fec.gov/info/contriblimitschart1516.pdf

http://www.fec.gov/pages/brochures/citizens.shtml

If I am wrong, I welcome corrections, but I think you're off on what corporations can and cannot do.