We all know that candidates for the Presidency and Congress alike are making the calls to the small, elite group of donors known for writing four-figure checks in election years. But other major avenues for political money are the independent 527 groups who can raise an unlimited amount of money and spend it at will, provided they follow requirements to disclose the source of that money.

With donations to federal candidates and political parties limited, 527s have come to occupy and increasing slice of the political advertising landscape:

Independent groups that aren't controlled by political parties or candidates have raised more than $120 million this election cycle, according to the non-partisan Center for Responsive Politics. These outside groups probably will raise and spend many more millions on TV and radio advertising, automated phone calls, mailed brochures, Internet sites and other politicking. Total spending by them was more than $433 million during the 2004 presidential campaign.

One of the reasons Senator Obama cited for opting out of the presidential public financing system was the fear that he wouldn't have the resources to counter ads and messaging from 527s. Yet another reason that Congress should look at a Clean Elections model for their elections and the presidential election -- with Clean Elections public financing, candidates receive additional funding to match expenditures from 527 groups and ensure that money doesn't determine what voices are heard -- or not heard -- on the campaign trail.