Chelsea Clinton (l.) and former US Secretary of State Hillary Rodham Clinton participate in a 'No Ceilings Conversation' at the Lower Eastside Girls Club in New York April 17, 2014. Chelsea Clinton recently announced that she and her husband are expecting their first child.
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Women line up for former US Secretary of State Hillary Clinton to sign copies of her book 'Hard Choices' at a Barnes & Noble bookstore in Los Angeles on June 19, 2014.
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Matt Barnard/Tulsa World/AP
Mrs. Clinton listens as teacher Brittany Holland reads a book with Cecilia Castillo March 24, 2014, at the Tulsa, Okla., Educare No. 2 site.
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Campaign buttons are ready for distribution at an Iowa kickoff event for the national Ready for Hillary group in Des Moines, Iowa, Jan. 25, 2014. Ready for Hillary is a 'super' political action committee that is building a national network to benefit Mrs. Clinton if she seeks the Democratic nomination for president in 2016.
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J Pat Carter/AP
Former Secretary of State Hillary Rodham Clinton (l.) and University of Miami President Donna Shalala (a former secretary of Health and Human Services under President Bill Clinton) share a laugh while speaking at the University of Miami in Coral Gables, Fla., Feb. 26, 2014.
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P. Kevin Morley/Richmond Times-Dispatch/AP
Hillary Rodham Clinton, a former US senator and former US secretary of State, and former President Bill Clinton share a moment under an umbrella before the rainy inauguration of Virginia Gov. Terry McAuliffe (D) in Richmond, Va., Jan. 11, 2014. The umbrella came from the five-star Jefferson Hotel.
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Former Secretary of State Hillary Clinton (l.) and Georgetown University President John DeGioia (r.) applaud after presenting the university's annual Hillary Rodham Clinton Award for Advancing Women in Peace and Security to Dr. Denis Mukwege, founder of the Panzi Hospital in war-ravaged Democratic Republic of the Congo, at Georgetown University in Washington, Feb. 25, 2014.
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Cory Morse/The Grand Rapids Press/AP
Supporters of former Secretary of State Hillary Rodham Clinton stand outside DeVos Place in Grand Rapids, Mich., where she was scheduled to speak at the Economic Club's annual dinner on June 17, 2013. Many hope Mrs. Clinton will run for president in 2016, but she hasn't announced her candidacy.
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Secretary of State Hillary Clinton talks with workers as she visits Partners in Health Cholera Treatment Center in Port-au-Prince, Haiti, on Jan. 30, 2012.
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First lady Michelle Obama (from l. to r.) joins former first ladies Laura Bush, Hillary Clinton, Barbara Bush, and Rosalynn Carter as they attend the dedication ceremony for the George W. Bush Presidential Center in Dallas, April 25, 2013.
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Pete Souza/White House/Reuters
President Obama (2nd l.) and Vice President Joe Biden (l.), along with members of the national security team, receive an update on the mission against Osama bin Laden in the Situation Room of the White House, May 1, 2011. Also pictured are Secretary of State Hillary Clinton (2nd r.) and Defense Secretary Robert Gates (r.).
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Secretary of State Clinton and former President Bill Clinton greet President Barack Obama during his ceremonial swearing-in on Capitol Hill in Washington on Jan. 21, 2013.
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Actress Meryl Streep uses her iPhone to get a photo of her and Secretary of State Hillary Rodham Clinton after the State Department Dinner for the Kennedy Center Honors gala at the State Department in Washington, Dec. 1, 2012.
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President Obama and Clinton toured the Sultan Hassan Mosque in Cairo in June 2009.
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Democratic presidential nominee Barack Obama, a US senator from Illinois, and Sen. Hillary Clinton (D) of New York attend a campaign rally in Orlando, Fla., on Oct. 20, 2008. Earlier in the year, Obama defeated Clinton to win the Democratic Party's nomination.
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Secretary of State Hillary Clinton calls a time-out during a multiple question from an Indian journalist, as India's Foreign Minister S.M. Krishna smiles during their news conference at the US-India Strategic Dialogue in Washington, D.C., June 13, 2012.
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Melanie Stetson Freeman/Staff
Senator Clinton speaks at the Democratic National Convention in Denver on Aug. 28, 2008.
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Democratic presidential candidate Senator Clinton smiles at her Ohio and Texas primary election night rally in Columbus, Ohio, March 4, 2008.
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Senator Clinton, with husband, Bill Clinton, and daughter, Chelsea, peers around Vice President Al Gore at a throng of photographers as she re-creates the oath of office to the US Senate in Washington, Jan. 3, 2001.
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Senator Clinton stands with Debbie Stabenow (l.) and Maria Cantwell, fellow freshmen US senators from the Democratic Party, during a press conference in Washington, Dec. 6, 2000.
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First lady Clinton watches President Clinton pause on Dec. 19, 1998, as he thanks those Democratic members of the House of Representatives who voted against his impeachment.