United States Senate

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Rick Weiland, the Democratic candidate for one of South Dakota's two U.S. Senate seats, talks about the Medicare Choice Act he plans to introduce if elected, Tuesday, Feb. 4, 2014, in Sioux Falls, S.D. (AP Photo/Dirk Lammers)

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FILE - This Oct. 15, 2013 file photo shows Dan Sullivan announcing a U.S. Senate bid in Anchorage, Alaska. Sullivan recently commented on raising the minimum wage. (AP Photo/Mark Thiessen, file)

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Scott Brown leads GOP hopefuls for a U.S. Senate seat from New Hampshire in a primary match-up, according to a new survey. (SCOTTBROWN.COM)

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U.S. Senate candidate Matt Bevin speaks at a meet and greet, Tuesday Jan. 14, 2014 in Henderson, Ky. The Louisville businessman is running against Senate Republican Leader Mitch McConnell in Kentucky's GOP primary next May. (AP Photo/The Gleaner, Mike Lawrence)

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Democratic U.S. Senate candidate Terry Adams, a Knoxville attorney, introduces himself at a press conference in Nashville, Tenn., on Friday, Jan. 10, 2014. (AP Photo/Erik Schelzig)

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Democratic U.S. Senate candidate Terry Adams, a Knoxville attorney, introduces himself at a press conference in Nashville, Tenn., on Friday, Jan. 10, 2014. (AP Photo/Erik Schelzig)

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Democratic U.S. Senate candidate Terry Adams, a Knoxville attorney, introduces himself at a press conference in Nashville, Tenn., on Friday, Jan. 10, 2014. (AP Photo/Erik Schelzig)

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Former Alaska Gov. Sarah Palin speaks at a rally for U.S. Senate candidate Steve Lonegan in New Egypt, N.J., on Saturday, Oct. 12, 2013. (AP Photo/Julio Cortez)