We the corporate campaign donors?
I remember the billboard controversy in Tucson in the 1980s described in Ray Ring's story (HCN, 1/23/12, "Billboards vs. Democracy"). As a scientist, I try to look for simple, logical solutions to problems. My take on corporate money in politics is a simple one. We, the voters, elect someone to represent us. If a candidate receives money from anyone or anything other than a voter who is eligible to vote for them, the obvious motive for the donation is to sway that candidate to represent someone (or something) other than who (or what) he or she is supposed to represent.
Corporations can't vote -- yet. Hence, any contribution made by a corporation to a candidate is a blatant attempt to get that candidate to represent its corporate interests rather than the interests of the people. That is a corruption of the political process.
The solution is simple: Only voters eligible to vote for a candidate should be permitted to contribute to that candidate. Political ads identifying a candidate should be considered contributions.
It is not a perfect solution, but it's way better than what we have now.