Election 2012 is set to be the most expensive in US history costing a whopping $6 billion with President Barack Obama and challenger Mitt Romney's campaigns alone spending $2.6 billion.

That tops the record set in 2008 by $700 million, according to a new analysis by Washington based research group Centre for Responsive Politics that tracks the effects of money and lobbying on elections and public policy.

Accelerating spending by ostensibly independent outside groups in the final weeks of the 2012 campaign is pushing the cost up with Romney being the main beneficiary with more than three-quarters of the money being spent on his behalf.

The major force behind the increased spending are hundreds of "super PACs", a new kind of political action committees that came into being after a federal court ruling in July 2010 lifted the ban on corporate political activity and permitted wealthy donors to pool unlimited sums of money for election spending.

In all, CRP estimates that expenditures by outside groups will reach more than $970 million this election. That's more than three times the previous record of $301 million in 2008.

And the total does not include tens of millions of dollars spent by tax-exempt advocacy group on issue ads and other forms of voter outreach that do not have to be reported to the Federal Election Commission.

What remains unknown-and may never fully be accounted for-is how much money secretive "shadow money" organizations spent, CRP said.

"One thing we can say for certain is that the transparency the Supreme Court relied upon to justify this new framework has been sorely lacking," said CRP executive director Sheila Krumholz.

The sources for money fuelling the presidential campaign in 2012 reflect the same basic interests led by finance, Insurance and Real Estate, Lawyers and Lobbyists, and Miscellaneous Business interests as in 2008.

But there was one big difference. To date, Romney holds an advantage over Obama among financial interests by a margin of 5-to-2, CRP said.

Indian-American community too has raised money for both campaigns, but they have contributed more to the Obama Campaign though far less than in 2008.

According to the Obama campaign half a dozen Indian-American bundlers have raised between half-a-million to one million dollars each and some others including new age guru Deepak Chopra have raised between $100,000 and $200,000.

An Indian American Coalition is estimated to have raised $15-20 million for Romney campaign with Florida-based Dr Akshay Desai alone raising $1 million.

Meanwhile, according to the CRP analysis, spending in congressional races is projected to increase slightly in 2012. House and Senate candidates combined will spend about $1.82 billion, up from $1.81 in 2010.

House campaign spending alone will total nearly $1.1 billion, a slight increase of 3 percent more over 2010. In the Senate, spending by candidates will approach $743 million, which is down about 7 percent compared to 2010.

Republican House candidates have also raised more on average-$712,000 to $594,000, --though Democrats did better than Republicans in the Senate, on average, raising $3.8 million to Republicans' $2.6 million on average.

All the five Indian-American Congressional candidates - Democrats Ami, Upendra Chivukula, Manan Trivedi and Syed Taj and Republican Ranjit Ricky Gill-are reported to have outraised their opponents.

Topping the list is Bera who has collected almost $2.7 million closely followed by Gill, who has raised more than $2.3 million.