Sen. Bernie Sanders (center) reaches out to supporters after speaking at a get-out-the-vote canvass launch at the City College of San Francisco ahead of last week's California primary.
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.
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California Gov. Jerry Brown speaks at the 91st Annual Sacramento Host Breakfast earlier this month. Brown endorsed Democrat Hillary Clinton ahead of his state's primary next week.
Democratic presidential candidate Bernie Sanders addresses a rally Wednesday at the Santa Clara County Fairgrounds in San Jose, Calif. The senator's campaign is intently focused on a big win in the state on June 7, and has poured money into TV ads there.
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U.S. Democratic presidential candidate Bernie Sanders leaves the Vatican Friday. Sanders went to Rome to attend a conference sponsored by the Pontifical Academy of Social Sciences.
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Hillary Clinton and Bernie Sanders both showed flashes of animosity bordering on contempt during Thursday's Democratic presidential primary debate in Brooklyn. The New York state primaries are Tuesday.
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Democratic presidential candidate Hillary Clinton argues a point as Sen. Bernie Sanders reacts during Sunday's Democratic presidential primary debate at the University of Michigan, Flint.