Tea Party activists gather on Capitol Hill in 2011. A surge in applications for 501(c)(4) status in recent years has revealed sometimes murky and contradictory rules governing the political activities of tax-exempt groups. Brendan Smialowski/AFP/Getty Images hide caption

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Republican U.S. Senate candidate Dan Winslow of Massachusetts wants same-sex married couples to have the same right to pool their money for political donations as other married couples. But the Federal Election Commission says the Defense of Marriage Act won't allow it. The constitutionality of DOMA is now before the Supreme Court. Charles Krupa/AP hide caption

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Senators Lisa Murkowski, an Alaska Republican, and Ron Wyden, an Oregon Democrat, discussing their new campaign finance legislation at an April 23, 2013 Capitol Hill news conference. Chip Somodevilla/Getty Images hide caption

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A woman views a Mitt Romney campaign ad in September, a month after the launch of an online government database that is supposed to make it easier for the public to see what political ads air in big markets, and how much is spent on them. Karen Bleier /AFP/Getty Images hide caption

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Former Alaska Gov. Sarah Palin addresses the Conservative Political Action Conference at the Marriott Wardman Park Hotel in Washington, D.C., last year. Mark Wilson/Getty Images hide caption

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David Koch, executive vice president of Koch Industries, attends an event at The Economic Club of New York last year. Mark Lennihan/AP hide caption

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The Supreme Court denied the petition of businessmen who say the 2010 Citizens United ruling makes it legal for corporations to contribute directly to candidates. The court building is seen here during renovations in December. Alex Wong/Getty Images hide caption

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The U.S. Supreme Court agreed to hear a challenge to campaign-finance laws that could open the door to further money in politics beyond what Citizens United achieved. Chip Somodevilla/Getty Images hide caption

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Sen. Robert Menendez of New Jersey, shown in June, has come under scrutiny before, but has never been charged. Mike Coppola/Getty Images hide caption

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Screenshot of a 2012 TV ad, featuring actor Clint Eastwood for Mitt Romney, by the Republican group American Crossroads. Screenshot of American Crossroads Ad hide caption

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Tourists take photographs in front of the U.S. Capitol on Jan. 2, the day after Congress passed a bill to avoid the fiscal cliff. Saul Loeb/AFP/Getty Images hide caption

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At a news conference last month, New York City Mayor Michael Bloomberg stands with people who have been affected by gun violence. John Moore/Getty Images hide caption

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Construction was under way on Capitol Hill in November for President Obama's Inauguration Day ceremonies. J. Scott Applewhite/AP hide caption

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