At the chamber, officials contend that rising donations are less the result of the recent Supreme Court ruling than they are of a 5-4 decision in 2007 in which the court ruled it was unconstitutional to ban issue-related advertising close to an election.
As a result of that ruling, the chamber was able to spend $1 million on so-called issue ads in the final days of the Massachusetts Senate race in January to help elect Scott Brown, the state's first Republican senator in decades.
As ominous music played in the background of one of the ads, a moderator intoned: "Washington politicians continue to fail us. More spending and fewer jobs. Scott Brown . . . supports measures that hold spending and cut taxes. . . . Call Scott Brown. Thank him."
Powerful as the effect of such advertising could be, the chamber and its allies expect the next big expansion of influence will come in street-level organizing and voter turnout operations.
Miller, a former chief of staff to a GOP lawmaker and co-owner of a restaurant in Washington's tony Georgetown section, built up the chamber's grass-roots organization in 2008 and expanded it in 2009 with the help of consulting firms.
Studying magazine subscriptions, voter registration and consumer buying habits, the consultants built a list of potential allies in 122 key congressional districts.
Individuals were invited to join the Friends of the U.S. Chamber initiative and were promised updates and special insights on Washington. They were then "activated," asked to write letters or call Congress on a particular issue or get involved in events in the districts.
Miller said the so-called activation rate was "roughly equivalent" to the rate claimed by Organizing for America, the network known as Obama for America during the presidential campaign, which has twice as many members.
The chamber has also given its staff, especially senior leaders, incentives to push fundraising. They are now working, in effect, on a commission system: the more money they bring in, the more they are compensated.
Officially, the chamber is a bipartisan nonprofit organization, but over the last decade it has tilted decidedly toward the Republicans. During 2008, 86% of the spending by the chamber's political action committee went to Republicans. Far more was spent on issue ads, most supporting GOP candidates.
The chamber says it represents 3 million companies that pay dues to the national chamber or a local affiliate, though internal documents suggest the organization's treasury is filled in substantial part by contributions from a couple dozen major corporations most affected by Washington policymakers.
Tax records from 2008 show that 19 companies or individuals paid between $1 million and $15.3 million, providing a third of the chamber's total revenue that year. Because the chamber is a nonprofit, it must disclose donations, but not necessarily the identity of the donors.
The chamber insists that those donors remain anonymous.
Some labor-backed organizations, such as Working America, which has 3 million nonunion members nationwide, have also declined to release details of its donors, which suggests a rocky road for legislation to require more transparency.
Kim Geiger of the Washington bureau contributed to this report.