Former Maryland Governor Martin O'Malley as he announces his intention to seek the Democratic presidential nomination during a speech in Federal Hill Park in Baltimore, Maryland. Jim Bourg/Reuters/Landov hide caption

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Bob Schieffer on the set of Face the Nation in September. Chris Usher/CBS hide caption

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Democratic presidential candidate and U.S. Sen. Bernie Sanders (I-VT) delivers remarks at a town meeting at the South Church May 27, 2015 in Portsmouth, New Hampshire. Win McNamee/Getty Images hide caption

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While governor of Texas, Rick Perry refused to accept federal funds to expand Medicaid. Rick Wilking/Reuters/Landov hide caption

itoggle caption Rick Wilking/Reuters/Landov