Prudential Financial sent in a $2 million donation last year as the U.S. Chamber of Commerce kicked off a national advertising campaign to weaken the historic rewrite of the nation’s financial regulations.

Dow Chemical delivered $1.7 million to the chamber last year as the group took a leading role in aggressively fighting proposed rules that would impose tighter security requirements on chemical facilities.

And Goldman Sachs, Chevron Texaco, and Aegon, a multinational insurance company based in the Netherlands, donated more than $8 million in recent years to a chamber foundation that has been critical of growing federal regulation and spending. These large donations — none of which were publicly disclosed by the chamber, a tax-exempt group that keeps its donors secret, as it is allowed by law — offer a glimpse of the chamber’s money-raising efforts, which it has ramped up recently in an orchestrated campaign to become one of the most well-financed critics of the Obama administration and an influential player in this fall’s Congressional elections.

They suggest that the recent allegations from President Obama and others that foreign money has ended up in the chamber’s coffers miss a larger point: The chamber has had little trouble finding American companies eager to enlist it, anonymously, to fight their political battles and pay handsomely for its help.