If the airwaves seem fuller than ever of political attack ads this campaign season, thank the U.S. Supreme Court.

A 5-4 decision early this year struck down the century-old ban on corporations and unions tapping their treasuries to influence elections. This has opened a floodgate of cash.

It's not just the court ruling, though, that is polluting this election's air: The stench of secrecy surrounds much of the cash that is turning this into the priciest mid-term election ever.

Organizations, such as the U.S. Chamber of Commerce and one founded by Bush strategist Karl Rove, are taking advantage of their tax-exempt status to avoid disclosing the sources of the money they are pouring into political races.

In Kentucky, the U.S. Chamber of Commerce (which is not your father's hometown chamber) and one of the Rove groups, Crossroads Grassroots Policy Strategies, had spent almost $1.9 million at last count against Democrat Jack Conway in the U.S. Senate race with Republican Rand Paul. Neither group discloses its donors.

Altogether, independent groups, some of which do disclose donors, had spent $2.6 million against Paul and $5.3 million against Conway, according to Federal Elections Commission data collected by the Sunlight Foundation.

(ABC reported last week that the banker for one of the Rove groups, American Crossroads, is Kentuckian Terry Forcht, who owns a nursing home in Hazard that Conway's office is prosecuting for covering up the sexual abuse of an elderly resident.)

Republicans across the country are benefitting more than Democrats this year from the surge in anonymous spending.

But two years ago, it was Democrats who figured out how to avoid contribution limits and disclosure requirements by steering contributions around campaigns and political parties, into innocuous sounding non-profits or political committees.

So, after this election, members of both parties who believe a democracy should be as free as possible from control by secret special interests should get behind reforms to increase disclosure.

With so much anonymous cash flooding the system, voters have no way of knowing who's trying to influence them to support a candidate.

But nothing keeps the donors from making sure candidates know who's putting up the money — and what they expect in return. Cynics may say we already have a government owned by the highest bidders. Just wait until we have a government owned by the highest secret bidders.

Soliciting secret cash donations from corporations was at the heart of the scandal that brought down President Richard Nixon almost 40 years ago. Now this corrupting force has been legitimized by a combination of the Supreme Court ruling and the FEC's limp policies on disclosure.

Significantly, the Supreme Court by 8-1 upheld disclosure requirements in federal election law at the same time it allowed unlimited corporate spending.

Justice Anthony Kennedy even wrote that transparency would counter the corrupting influence of unlimited corporate money. "With the advent of the Internet, prompt disclosure of expenditures can provide shareholders and citizens with the information needed to hold corporations and elected officials accountable for their positions."

But current law falls far short of providing the degree of transparency that he described. The House of Representatives this year approved strengthening disclosure requirements, but Republicans in the Senate killed the measure.

Full disclosure as an antidote to corruption was the condition on which Sen. Mitch McConnell built his long crusade against limits on political spending. Until recently, that is.