A new analysis projects that by Election Day, non-party, non-candidate groups will likely spend more than a half billion dollars to influence the congressional campaigns.
It's just the latest report documenting a surge in undisclosed political money this year.
With two weeks to go till election day interest groups have already spent more than they did in the 2008 congressional races.
The analysis comes from the non-partisan Campaign Finance Institute -- which now projects that the so-called independent groups will end up spending around $564 million this year.
That's up 40 percent from two years ago. Most of the additional money appears on the conservative side.
The institute projects that ultimately about $334 million will be spent to help Republican candidates.
That's about $100 million more than pro-Democratic groups are likely to spend -- a reversal from 2006 and 2008... when liberal groups dominated the money race.
Institute Director Michael Malbin said it's impossible to judge the impact of Citizens United -- the Supreme Court decision that made it easier for corporations and unions to spend money in politics.
Much of the money is being raised by three pro-Republican groups - Crossroads GPS, American Action Network and the Commission on Hope Growth & Opportunity.
The American Action Network said today it's launching TV and Internet ads in 21 Democratic congressional districts. The group didn't put a price tag on the media blitz.
Nor did it disclose the donors behind it.