US November mid-term elections are on track to be the costliest ever after controversial high court rulings opened the way for shadowy donors to flood key races with cash aimed at shaping the outcome.
"This will easily set spending records for US mid-term elections," according to Dave Levinthal, spokesman for the independent Center for Responsive Politics that tracks the influence of money in US politics.
The center puts the price tag for this election cycle at about 3.4 billion dollars and rising, compared to 2.9 billion for the 2006 mid-terms, 2.2 billion for the 2006 mid-terms, and 1.6 billion for the mid-terms in 1998.
Analysts have given Republicans strong odds of gaining the 39 seats they need to retake the House of Representatives, and even a long shot at capturing the 10 seats they need to seize the Senate.
All 435 House of Representatives seats are up for grabs in the election, as are 37 of the 100 Senate seats and many key governorships.
The cash totals include all money spent by Senate and House candidates, political parties, and independent interest groups, which have proliferated this year after a pair of US Supreme Court rulings lifted campaign finance curbs.
It's all private money. Public funding is only available to US presidential candidates, and only if they agree to overall spending limits, as well as to defray costs tied to the two major parties' nominating conventions.
US law sets some limits on how much an individual can give per election cycle: 2,400 dollars to a candidate, 30,400 dollars to a national party, and 5,000 to a nominally independent "political action committee" or PAC.
But the US Supreme Court's "Citizens United" decision in January and the "SpeechNow.org v. FEC" ruling in March have given corporations, labor unions, and advocacy groups a free hand to spend unlimited sums on independent campaigns for, or against, a given candidate.
The resulting "Super-PACS" can raise unlimited amounts from individuals, corporations, unions and other groups, and in some cases keep their donors entirely anonymous.
President Barack Obama's Republican foes earlier this year defeated a Democratic bill that would have required naming major contributors, a direct response to the rulings by the most conservative US high court in decades.
The result has been an unprecedented flood of cash from wealthy interests.
Last week Obama stepped up his attack on the flood of outside money, often from unidentifiable sources and much of it financing opposition Republicans.
"It could be the oil companies. It could be the insurance industry. It could be Wall Street. You don't know. Their lips are sealed. The floodgates are open, though," Obama said at a Democratic campaign rally in Maryland.
But Republicans maintain the court rulings reflect the US Constitution's guarantee of freedom of speech.
Among the most prominent "Super-PACS" is a group called American Crossroads, founded by former president George W. Bush's top political strategist, Karl Rove, and former senior Bush adviser Ed Gillespie.
It plans to spend some 52 million dollars to help Republicans, has targeted 10 Senate races and plans "considerable" spending on House battles, spokesman Jonathan Collegio told AFP.
Campaign funding is the lifeblood of US politics, notably critical to buying costly television ads needed to boost name recognition, according to Matt Dickinson, a political scientist at elite Middlebury College in Vermont.
In the 2008 election cycle, the better-funded candidate won in about 93 percent of House and Senate races, Dickinson told AFP, adding: "Does it mean you can buy elections? I'm not sure you can go that far."
"Money buys access. If you're a huge campaign donor and you want to bend your representative's ear for an hour, and they open the books to find your a serious support, sure," he said.
Among occupations, retirees have given the most in the 2010 cycle, with 98.5 million dollars spread roughly evenly between Democrats and Republicans, ahead of lawyers and law firms, who have favored Democrats with their 98 million, according to the Center for Responsive Politics.
Super-rich Americans can fund their own campaigns, as former professional wrestling executive Linda McMahon has done, pouring some 22 million dollars into her Senate bid in Connecticut.
Democratic House and Senate candidates have raised a total of 362 million dollars and 229 million dollars, according to the Center for Responsive Politics, against 365 million and 239 million by Republicans.
The number two House Republican, Representative Eric Cantor, has raised the most, with nearly 4.7 million dollars, and leads the pack in candidate-to-candidate donations, according to the center.
Democratic Representative Vic Snyder was at the other end of the scale, raising just 347 dollars -- but he is not seeking reelection.