Democratic presidential candidate Bernie Sanders speaks during a rally in Washington, D.C., on June 9. Although he didn't win the nomination, Sanders' grass-roots fundraising has broken records. Alex Wong/Getty Images hide caption

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Will The Millions Of People Who Gave Money To Bernie Sanders Give To Democrats?

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Colorado Democrats pack a gym at a Denver high school during caucuses on March 1, 2016. The crowds and long lines have led to calls for the state to move to an open primary system. Marc Piscotty/Getty Images hide caption

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Americans Don't Like Caucuses, But Replacing Them With Primaries Isn't Easy

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Vice President Hubert Humphrey (right) and his running mate, Sen. Edmund S. Muskie, wave to the crowd with their wives at the Democratic Convention in Chicago on Aug. 29, 1968. Violence ensued inside and outside the convention hall. AP hide caption

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Republican presidential candidate Sen. Ted Cruz is joined by former Hewlett-Packard CEO Carly Fiorina during a rally in Indianapolis on Wednesday. Cruz announced he has tapped Fiorina to serve as his running mate. Michael Conroy/AP hide caption

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Hillary Clinton addresses supporters after winning four of five Northeastern states Tuesday night. Eduardo Munoz Alvarez/AFP/Getty Images hide caption

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