President Franklin D. Roosevelt and his Republican challenger, Kansas Gov. Alfred M. Landon (left), meet in September 1936. AP hide caption

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An unidentified heckler lets loose as President Obama begins a speech at the Martin Luther King memorial dedication in Washington, D.C., in October 2011. Mannie Garcia/UPI/Landov hide caption

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While American politicians may be scripted, they're not this robotic. But whoever wins the presidency this year will preside over a U.S. economy where automation is becoming increasingly important. iStockphoto hide caption

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The infield at Churchill Downs can get pretty beer-soaked, as this scene from the 2011 Kentucky Derby proves. But this year, things could get even more crazy: The Derby falls on another of America's favorite "alcoholidays," Cinco de Mayo. Matt Slocum/AP hide caption

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Former Massachusetts Gov. Mitt Romney and President Obama will spend the next six months highlighting their differences. But they also share some striking similarities. Chip Somodevilla/Olivier Douliery/Getty Images hide caption

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Republican presidential hopeful Ronald Reagan, right, listens to the Rev. Jerry Falwell during a campaign stop in Lynchburg, Va., in October 198 Charles Harrity/AP hide caption

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President Obama inspires strong feelings, some positive, some negative. This composite image shows Obama at two separate events. AP and Getty Images/NPR hide caption

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An enumerator interviews a woman for the 1940 census. Veiled in secrecy for 72 years because of privacy protections, the 1940 U.S. census is the first historical federal decennial survey to be made available on the Internet initially rather than on microfilm. National Archives at College Park hide caption

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James Gilchrist of Orlando, Fla., attends a rally for slain teenager Trayvon Martin in Sanford, Fla., on Thursday. Trayvon was wearing a hoodie when he was shot. Roberto Gonzalez/AP hide caption

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