Democratic presidential candidate Bernie Sanders waves to the crowd after arriving Tuesday at a campaign rally at the Big Four Lawn Park in Louisville, Ky. John Sommers II/Getty Images hide caption

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Bernie Sanders Says He's Staying In And It's 'Good For The Democratic Party'
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Sen. Bernie Sanders waves to a crowd gathered at Gettysburg College in Gettysburg, Pa., on Friday. Pennsylvania holds its presidential primary Tuesday. Mark Wilson/Getty Images hide caption

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Sanders Adviser Says Campaign May Have To 'Re-Evaluate' After Tuesday
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Presidential candidate Bernie Sanders, I-Vt., walks offstage to greet the massive crowd gathered in New York's Washington Square Park on Wednesday. The Washington Post/The Washington Post/Getty Images hide caption

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Sen. Bernie Sanders speaks during a political rally on April 5 in Laramie, Wyo. Sanders spoke to a large crowd on the University of Wyoming campus after winning the Wisconsin primary. Theo Stroomer/Getty Images hide caption

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Bernie Sanders, I-Vt., pumps his fist during a campaign rally in Laramie, Wyo., Tuesday. Brennan Linsley/AP hide caption

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After Wisconsin, Demographics Suggest Rougher Terrain For Sanders, Cruz
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US Democratic presidential candidates Hillary Clinton (R) and Bernie Sanders smile after participating in the MSNBC Democratic Candidates Debate at the University of New Hampshire in Durham on February 4, 2016. Jewel Samad/AFP/Getty Images hide caption

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Has Bernie Sanders Pulled Hillary Clinton To The Left?
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