Concertgoers move in a spray of cooling mist as they dance amid the heat of the desert at the hipster Coachella Valley Music & Arts Festival in Indio, Calif., in April. Mike Blake/Reuters /Landov hide caption

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Republican presidential candidate Herman Cain speaks Monday at the National Press Club in Washington, D.C. During a question and answer portion of the program, Cain called the accusations of sexual harassment against him "a witch hunt."

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Herman Cain (right) speaks as Texas Gov. Rick Perry looks on during a GOP presidential debate at Dartmouth College on Oct. 11.

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Rep. Michele Bachmann greets supporters after Tuesday's debate in New Hampshire. She saw her political fortunes rise earlier in the summer but has since fallen back in the polls.

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The type of atomic bomb that was used in Japan in World War II, known as the "Fat Man," is shown here in a 1960 photo released by the U.S. government. Liberals and conservatives are gathering at the Ronald Reagan Presidential Library on Tuesday to call for efforts to eliminate nuclear weapons.

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Obama is surrounded by former presidents in the Oval Office in 2009. Two of his predecessors — George W. Bush and Bill Clinton — won two terms, while two others — George H.W. Bush and Jimmy Carter — left office after just one.

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Former Utah Gov. Jon Huntsman (right) and Texas Gov. Rick Perry confer during a break in the Sept. 12 presidential debate in Tampa. Huntsman first objected to Perry's use of the word "treasonous" then later used it himself.

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Fans of the Tampa Bay Rays celebrate during the singing of "God Bless America" during the game against the Boston Red Sox at Tropicana Field on Sept. 11 in St. Petersburg, Fla. J. Meric/Getty Images hide caption

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