At issues is a Supreme Court ruling earlier this year — criticized by President Barack Obama and Democrats — that relaxed campaign finance rules, allowing unlimited contributions from corporations and special interest groups.

Criticism about the US Chamber of Commerce, one of Washington’s most influential lobbying groups, reached a new pitch Sunday in an already surprisingly heated national debate about campaign finance.

The foreign-money angle about the Chamber comes from a report released last week by ThinkProgress, an arm of the liberal Center for American Progress’ think tank. The foreign-money angle springs from allegations that the chamber collects dues from more than 100 overseas business councils — known as “AmChams” — that are funneled into its general fund, which is also the source of funding for the group’s political activities in the United States. It said AmCham has pledged to spend $75 million to defeat Democratic gubernatorial House and Senate candidates in the November mid-term elections — a dollar figure that towers over the campaign spending of other outfits. The exposé found that this money will come from AmCham’s general account “which solicits” funds from foreign corporations and governments. ThinkProgress said it had identified $300,000 in dues from the AmCham in Bahrain alone since 2006 and questioned whether the chamber was improperly co-mingling the dues with political funds. As the report notes, BP and other foreign corporations are active AmCham boosters but that support pales in comparison to the massive money AmCham raises from independent and government run corporations in foreign locales like “China, India, Egypt, Brazil, Russia and many other places” around the world.

The Chamber of Commerce and Crossroads GPS, a conservative group, have spent $33 million on campaign advertising so far. The chamber has said it plans to spend the money backing pro-business candidates and targeting the administration’s policies on health care, the environment and jobs.

AmCham said it spent at least $1 million per race targeting Senate candidate Paul Hodes (D) in New Hampshire; Sen. Barbara Boxer (D) in California; and Florida Gov. Charlie Crist, a disaffected Republican running as an independent against Marco Rubio (R) and Rep. Kendrick Meek (D). The group is also running ads against endangered Democratic Sen. Russ Feingold in Wisconsin and Democratic Senate candidate Richard Blumenthal in Connecticut, who is in an unexpectedly tight race with Linda McMahon, a former wrestling executive who is tapping her fortune for the campaign. On Sunday, a senior official in Obama’s administration called on the US Chamber of Commerce to prove that it is not funding campaign advertisements with foreign money.

David Axelrod, one of the president’s closest advisers, escalated a war of words with conservative and business groups, saying that secret donations to these organizations, including the Chamber of Commerce, were “a threat to our democracy.” Speaking on CBS’s Face the Nation Axelrod said: “If the Chamber opens up its books and says ‘here’s where our political money’s coming from,’ then we’ll know. But until they do that, all we have is their assertion.” Obama, speaking at a campaign rally in Philadelphia on Sunday, continued Axelrod’s attacks when he alluded to the US Chamber of Commerce and other conservative groups affiliated with Karl Rove, by saying: “The American people deserve to know who is trying to sway their elections” and raised the possibility that foreigners could be funding his opponents.

“You don’t know,” Obama said at the rally for Senate candidate Joe Sestak and other Democrats. “It could be the oil industry. It could even be foreign-owned corporations. You don’t know because they don’t have to disclose.”

Karl Rove also pushed back on the Sunday shows: Rove called Obama’s words a “desperate political ploy.” Chamber spokesperson Tita Freeman told reporters that it is “inaccurate” to claim that there is a “general fund” to begin with, and stressed the Chamber sees no need to share any additional detail about its inner workings.