While super PACs, seven-figure checks and the heated Republican presidential nomination fight that Mitt Romney eventually won dominated the news the first half of this election year, congressional campaigns quietly have been pumping hundreds of millions of dollars into the political economy -- and the real avalanche of congressional campaign expenditures and campaign ads is yet to begin.

Outside spending groups like the Campaign for Primary Accountability and Freedomworks for America have gotten most of the spotlight for running ads attacking incumbents in primaries. But congressional candidates themselves have had far more to spend to get their message out. As of ...