A polling station in Oakmont, Pa., on Nov. 6, 2012. Winning a presidential nomination includes mastering complex rules about delegates, and Pennsylvania's rules are among the most complicated.
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Bernie Sanders addresses a rally at Macomb Community College in Warren, Mich. Sanders needs a good showing in Michigan on Tuesday to start to turn his campaign around.
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Donald Trump greets supporters after speaking at a caucus night watch party at the Treasure Island Hotel & Casino in Las Vegas. Trump is favored to do well Super Tuesday.
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