U.S. Sen. Sherrod Brown (right), D-Ohio, debates his Republican challenger, Ohio state Treasurer Josh Mandel, at the City Club in Cleveland on Oct. 15. Tony Dejak/AP hide caption

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Democatic Rep. Shelley Berkley greets Republican Sen. Dean Heller before the second of their three debates, on Oct. 11 in Las Vegas. Julie Jacobson/AP hide caption

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Rep. Todd Akin, R-Mo., says Rep. Paul Ryan, R-Wis., the GOP vice presidential candidate, asked him to end his Senate bid after recent comments he made referring to "legitimate rape." Jeff Roberson/AP hide caption

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Massachusetts Senate candidate Elizabeth Warren is shown here attending a 2010 Capitol Hill hearing on the Troubled Asset Relief Program. Alex Wong/Getty Images hide caption

itoggle caption Alex Wong/Getty Images