US House and Senate candidates have surpassed fundraising records for the mid-term elections and are now nearing the $2bn (£1.2bn) spending mark, with elections just one week away.
The projection by Public Campaign Action Fund, a watchdog group, breaks down to $4m for each seat at stake.
Meanwhile, ex-President Bill Clinton is visiting Illinois in the hope of preventing Republican gains there.
President Barack Obama will join him on Saturday to rally Democratic voters.
With exactly one week to go before the mid-term elections, uncertainty surrounds the scope of widely anticipated Democratic losses in the House, the Senate, governor's races and state legislatures.
Congressional candidates for the House have raised 30% more money and spent 54% more in funds than candidates at the same point in the 2008 race, the Public Campaign Action Fund report says, based on data from the non-partisan Center for Responsive Politics.
In 2008, House candidates raised $978m (£617m) and spent $938m over the full election cycle.
This year, the Public Campaign Action Fund projects that House candidates will raise nearly $1.3bn and spend more than $1.4bn.
Mr Obama and Mr Clinton are hoping to influence voters in the traditionally Democrat-controlled state of Illinois on behalf of Alexi Giannoulias, the state treasurer hoping to claim Mr Obama's seat in the US Senate, and Governor Pat Quinn, who is seeking re-election.
Many Democrats hoping for a win in the 2 November elections continue to face a rough ride over the country's economic woes, for which many Republicans have criticised the president.
But to take control of the Senate, Republicans would have to win in a number of toss-up states, such as Mr Obama's home state of Illinois.
Some Democratic candidates have even declined campaign appearances by the president, whose approval rating has dropped significantly since taking office.
A Politico/George Washington University poll released this week shows independents are increasingly siding with Republicans - a dynamic change that could have a large impact on the outcome.
Meanwhile, 63% of Republicans and Republican-leaning registered voters say they are more enthusiastic than usual about the mid-terms, according to a USA Today/Gallup poll, whereas 37% of Democrats report more enthusiasm than usual about voting.
The heightened emotions became apparent on Monday night during a scuffle at a debate in Kentucky between Republican Senate candidate Rand Paul and Democratic opponent Jack Conway.
Mr Paul's supporters wrestled a liberal activist, Lauren Valle, to the ground and stepped on her head, after she tried to approach the candidate with a fake award.
The Paul campaign issued a statement describing the incident as "incredibly unfortunate" and stating that there was no place for violence in the democratic process.
The campaign volunteer responsible for stepping on the activist's head apologised on Tuesday.