Last fall, Oregon Rep. Peter DeFazio was the subject of a political ad paid for by the Concerned Taxpayers of America — which turned out to be a million-dollar front group financed by just two men. Read more about that ad, and how DeFazio followed the money. Jonathan Ernst/Getty Images hide caption

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Former House Speaker Newt Gingrich, speaking at a news conference Thursday in Atlanta, says he is launching a website to explore a run for president. Mike Stewart/AP hide caption

itoggle caption Mike Stewart/AP

Demonstrators gathered outside the Ohio Statehouse last week to protest Senate Bill 5, which would have banned collective bargaining for state workers. Unions say legislation being pushed by Republican governors nationwide is an attack on their very existence. Jay LaPrete/AP hide caption

itoggle caption Jay LaPrete/AP

The Koch Industries Inc. headquarters in Wichita, Kan. LARRY W. SMITH/ASSOCIATED PRESS hide caption

itoggle caption LARRY W. SMITH/ASSOCIATED PRESS

President Obama, shown answering questions during a news conference Tuesday, is expected to hit the billion-dollar mark in fundraising for his re-election bid. His Republican opponent may raise that much as well. Evan Vucci/AP hide caption

itoggle caption Evan Vucci/AP