Former Secretary of State Hillary Clinton speaks to a crowd during a book signing for her new book, Hard Choices. Clinton's book tour has brought her before admiring audiences, but also highlighted her difficulty talking about her wealth and her presidential vision. Andrew Burton/Getty Images hide caption

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Rubio, seen here addressing the National Press Club in May, told NPR he'll decide on a presidential run in the next few months Alex Wong/Getty hide caption

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Before talking about the situation in Iraq, President Obama bantered with (from left to right) Senate Minority Leader Mitch McConnell, House Speaker John Boehner, Senate Majority Leader Harry Reid and House Minority Leader Nancy Pelosi. Pablo Martinez Monsivais/AP hide caption

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Hillary Clinton promotes her new book, Hard Choices, in Chicago on Wednesday. The former senator and secretary of state had a lively and much-talked-about chat this week with Fresh Air's Terry Gross. Stacy Thacker/AP hide caption

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Hillary Clinton at a book signing in New York. The former secretary of state has said that Benghazi joins a long list of tragedies during administrations of both parties. Bebeto Matthews/AP hide caption

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Hillary Clinton poses for a family photo with former President Bill Clinton, daughter Chelsea, and son-in-law Marc Mezvinsky, after attending Chelsea's Oxford University graduation ceremony last month. Matt Dunham/AP hide caption

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Former White House intern Monica Lewinsky meets President Clinton at the White House on Dec. 16, 1996. Lewinsky, whose affair with Clinton eventually led to his impeachment, has written an article in Vanity Fair in which she talks about her life after the scandal. Getty Images hide caption

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Former Secretary of State Hillary Clinton ducks after a woman threw a shoe at her while she was delivering remarks at the Institute of Scrap Recycling Industries conference on Thursday in Las Vegas. Isaac Brekken/Getty Images hide caption

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Former Secretary of State Hillary Rodham Clinton and former President Clinton huddle under an umbrella during inaugural ceremonies for Virginia Gov. Terry McAuliffe in Richmond on Jan. 11. Patrick Semansky/AP hide caption

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The question isn't whether former Secretary of State Hillary Clinton will run for president in 2016 but whether she will stop, say the authors of a new book. Gerald Herbert/AP hide caption

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