Republican presidential candidates, Sen. Marco Rubio, R-Fla., left, Donald Trump, Sen. Ted Cruz, R-Texas, and Ohio Gov. John Kasich, right, stand together during the signing of the National Anthem, before the start of the Republican presidential debate Thursday in Miami. Wilfredo Lee/AP hide caption

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Democratic presidential candidate Sen. Bernie Sanders scored an upset win in Michigan on Tuesday. He's seen here speaking last week in Illinois, which holds its primary next Tuesday. Seth Perlman/AP hide caption

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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. Scott Olson/Getty Images hide caption

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Marco Rubio and Donald Trump participate in the Republican presidential debate in Detroit. Geoff Robins/AFP/Getty Images hide caption

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Marco Rubio Defends His 'Small Hands' Criticism Of Donald Trump
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Donald Trump addresses a crowd in South Carolina. Trump has the clearest path to the GOP nomination, but Republicans opposed to him aren't giving up the fight. Spencer Platt/Getty Images hide caption

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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. Ethan Miller/Getty Images hide caption

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Republican presidential candidate Donald Trump speaks at his election night party February 20, 2016 in Spartanburg, South Carolina. The New York businessman won the first southern primary decisively. Spencer Platt/Getty Images hide caption

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Bernie Sanders and Donald Trump deliver victory speeches at their respective watch parties in New Hampshire. Jewel Samad/AFP; Joe Raedle/Getty Images hide caption

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Republican presidential candidates, from right, Ohio Gov. John Kasich, former Florida governor Jeb Bush and Sen. Marco Rubio, R-Fla., participate Jan. 28 in a GOP debate in Des Moines, Iowa. Rubio's strong third-place finish in Iowa has given him momentum and more backing from the same establishment Republicans that Bush and Kasich need for their campaigns to survive. Scott Olson/Getty Images hide caption

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Jeb Bush holds a campaign town hall meeting at the Alpine Club on Monday in Manchester, N.H. Chip Somodevilla/Getty Images hide caption

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Heading Into New Hampshire, GOP 'Front-Runners' Are Anything But
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Republican presidential candidate Marco Rubio speaks to a capacity crowd during a campaign event in Exeter, N.H. Steven Senne/AP hide caption

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Signs Of 'Marco-mentum' For Rubio In New Hampshire
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Democratic presidential candidate Hillary Clinton speaks at a rally in Marshalltown, Iowa. Clinton is narrowly ahead of Sanders, but within the margin of error in the final Iowa poll. Andrew Harnik/AP hide caption

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