I first heard of this on the Thom Hartmann show (via Think Progress blog):

The Chamber has promised to spend an unprecedented $75 million to defeat candidates like Jack Conway, Sen. Barbara Boxer (D-CA), Jerry Brown, Rep. Joe Sestak (D-PA), and Rep. Tom Perriello (D-VA). As of Sept. 15th, the Chamber had aired more than 8,000 ads on behalf of GOP Senate candidates alone, according to a study from the Wesleyan Media Project. The Chamber’s spending has dwarfed every other issue group and most political party candidate committee spending …

Previously, it has been reported that foreign firms like BP, Shell Oil, and Siemens are active members of the Chamber. But on a larger scale, the U.S. Chamber of Commerce appears to rely heavily on fundraising from firms all over the world, including China, India, Egypt, Saudi Arabia, Brazil, Russia, and many other places. Of course, because the Chamber successfully lobbied to kill campaign finance reforms aimed at establishing transparency, the Chamber does not have to reveal any of the funding for its ad campaigns. Dues-paying members of the Chamber could potentially be sending additional funds this year to help air more attack ads against Democrats.

Keith Olbermann also did a segment later on the day:

Update: following the trail of corporate greed, are you starting to wonder why foreign interests are investing massive amounts of money to take down certain progressive Senators and Representatives?  Well, it’s probably no coincedence that the Senators that are being targeted to be taken down support the Creating American Jobs and Ending Offshoring Act, which would make it more difficult for companies to ship off jobs overseas to exploit cheap labor instead of investing in our country and employing Americans.  Via Think Progress:

Senate Democrats tried to bring the Creating American Jobs and Ending Offshoring Act, which would give “companies…that shift overseas jobs to the U.S.” a special payroll tax holiday, to the floor for a full vote. Yet thanks to a united Republican filibuster and the defection of a handful of Democratic caucus senators — Max Baucus (MT), Ben Nelson (NE), Jon Tester (MT), Mark Warner (VA), and Joe Lieberman (CT) — the Democrats failed to achieve cloture and were unable to bring the bill up for a vote.

[…] the U.S. Chamber of Commerce declared its opposition to the bill, claiming that “replacing a job that is based in another country with a domestic job does not stimulate economic growth.” The National Association of Manufacturers (NAM) also came out against the bill, arguing it would “jeapordize” American job creation.