Six billion dollars. That's how much money has been blown to influence the US election race that reached the finish line with Tuesday's vote.

Raising six-figure sums at parties with Hollywood czars and hedge fund tycoons or small double-digit offerings via smartphone apps, Barack Obama, Mitt Romney and Congressional candidates have smashed records for campaign spending.

According to an estimate by the Center for Responsive politics, the two White House rivals spent $2.6 billion between them by election day.

Obama trumped his Republican rival in individual contributions, by late October raising $645 million to $413 million.

But the CRP had Romney ahead when all other spending in support of him was considered, from political action committees and other groups pitching for the candidates indirectly.

Surprisingly, the presidential race spending is lower than the $2.8 billion in 2008's White House race.

Instead, the big jump is spending on hundreds of Congressional elections, especially for the Senate, where close races raised the possibility that the Democrats could lose control of the upper house.

In all, the bill comes to $40 a vote, based on 2008's record turnout, 57 percent of the voting age population.

What the voters got, best understood by residents of swing states like Nevada, Florida and Ohio, has been a tsunami of advertisements on their televisions, radios, email accounts and Twitter feeds.

Spending was guaranteed to soar this year after the landmark Supreme Court "Citizens United" case decision in January 2010 said that corporations and unions are able to spend money to promote candidates just like individuals can.

That has allowed outside political action committees known as Super PACs to pump nearly $1 billion into the races, according to the CRP.

And then there are the unidentified sources of spending.

"What remains unknown -- and may never fully be accounted for -- is how much money secretive 'shadow money' organizations spent, with some investing massive sums on ads, but also on unreported and purportedly "non-political" activities, as the election neared. It may take years to determine how much they spent."

According to the CRP, Obama as before has relied more on small individual contributions than Romney, but large donors have been crucial for both.

Banks and their staff have been a key resource for Romney while academics and tech companies and their workers have been important to Obama.

Romney's top three sources of donations are Goldman Sachs and its employees; Bank of America, and Morgan Stanley.

For Obama it was the University of California, Microsoft and Google.

But in categories of employment, retired people were by far the largest source of donations, giving more than $50 million to each candidate.

This year new technology has pushed into the fund-raising in a big way: donating via one's phone.

A Pew Research Center survey in October found that 13 percent of all adults had donated to one of the presidential candidate, and of them 10 percent had contributed via a cell phone app or text message.

Donors, Pew said, are evenly split between Democrats and Republicans, but Democrats are far more likely to donate on line or via their phone.