More than any other election season in memory, the U.S. Chamber of Commerce has become a major player (if not THE major player) influencing the campaigns of those running for Congress.
That influence of course is not in direct support of candidates, but the political "issue" ads the Chamber sponsors make no doubt which candidate it supports and which one it criticizes, to wit over 90% are in support of Republicans.
Most of the donations the Chamber receives are from big corporate donors to which they keep secret and are not required to publically disclose. And why, one might ask is the Chamber able to keep their lists of donors secret? It is because they are listed as a 501(C) (6) tax exempt organization! That's right, the biggest lobbying operation in Washington is a tax exempt, non-profit organization.
The only reason disclosure of the Chamber's big donors is known is through the required tax filings and public records of the corporations making the donations. 
So through these tax filings we discover Prudential Financial gave $2 million, Dow Chemical $1.7 million, Goldman Sachs, Chevron Texaco and Aegon (a Netherlands based insurance company) gave over $8 million in the last few years, while the private health insurers gave over $10 million last year in opposition to Obama's health care reform legislation. 
Though no corporation openly acknowledges their contributions to the Chamber are aimed at specific legislation, it would the height of naivete' to believe otherwise as "many of those large donations coincided with lobbying or political campaigns that potentially affected the donors." 
Of late, many critics of the Chamber (including the president) have expressed their concern of funds (from big foreign donors to the Chamber's coffers) being used to support the politically directed ad campaigns that are specifically prohibited by law.
To this observer, what the Chamber of Commerce is engaging in is a giant money laundering operation supporting the interests of the mega corporations, domestic and foreign, that go to influence and support legislation and legislators who are beholden to these interests who then enact the laws and regulations that benefit these interests. And it's all legal.
What the Supreme Court did its 5 to 4 decision in the case of "Citizens United" v/s "FEC" was to open the floodgates for a torrent of cash by the corporate behemoths to overwhelm the election process in their favor. This legalized corruption of our elections by the big moneyed and special interests is all but complete.
Our only hope to rectify this corrupting bastardization of our elections is to have a constitutional convention to amend the Constitution to specifically eliminate corporate money in the election process.
Unless that comes to pass (the Congress or 32 states can call for a constitutional convention), American democracy of, by and for the people is dead. There is no other way to say it.