Candidates raised more than $1.2 billion through June, the latest figures indicate, surpassing the nearly $886 million collected at the same point in the 2006 elections, USA Today reported.
In a reversal from 2008, Republican House and Senate candidates have the edge, taking in nearly $49 million more than Democrats.
"We are on track to obliterate the spending levels of 2006," said Dave Levinthal of the Center for Responsive Politics.
About 75 percent of political advertising in House races occurs in the last 30 days, said Evan Tracey of the Campaign Media Analysis Group. "It's going to be coast-to-coast, wall-to-wall politics on your TV and radio this fall," he said.
Party committees and outside groups have spent $99 million on TV ads with pro-Republican messages since the start of 2009, compared with $63 million for Democratic parties and groups, Tracey said.
Spending by independent groups is helping Republicans overtake Democrats. The House Democrats' campaign arm ended July with nearly $14 million more on hand than its GOP counterpart.