CNN Republican debate: What's at stake for Republican 2016ers

The stage is set at the Reagan Presidential Library on September 13, 2015, for the CNN Republican Presidential Candidate Debate. CNN's Jake Tapper will be the moderator for the debate from the Library on the 16th.

CNN's debate rules, explained

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Tapper: 'Unbelievable' how quickly Trump took the bait

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CHARLESTON, SC - JANUARY 17: Democratic presidential candidates Martin OMalley (L), Hillary Clinton (C) and Senator Bernie Sanders (I-VT) participate in the Democratic Candidates Debate hosted by NBC News and YouTube on January 17, 2016 in Charleston, South Carolina. This is the final debate for the Democratic candidates before the Iowa caucuses. (Photo by Andrew Burton/Getty Images)

NBC Democratic presidential debate in 90 seconds

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Clinton, Sanders disagree on support of President Obama

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Debate reality check: Who was telling the truth?

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Bernie Sanders defends gun control record

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Clinton to Sanders: I'm not starting over on healthcare

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Sanders: 'The Democratic Party needs major reform'

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Trump: Cruz 'insulted 20 million people'

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Republican presidential candidates, from left, Ohio Gov. John Kasich, New Jersey Gov. Chris Christie, Sen. Marco Rubio, R-Fla., businessman Donald Trump, Sen. Ted Cruz, R-Texas, retired neurosurgeon Ben Carson and former Florida Gov. Jeb Bush take the stage before the Fox Business Network Republican presidential debate at the North Charleston Coliseum, Thursday, Jan. 14, 2016, in North Charleston, S.C. (AP Photo/Rainier Ehrhardt)

Fox Business GOP debate in 90 seconds

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WASHINGTON, DC - JANUARY 12: President Barack Obama delivers his State of the Union address before a joint session of Congress on Capitol Hill January 12, 2016 in Washington, D.C. In his final State of the Union, President Obama reflected on the past seven years in office and spoke on topics including climate change, gun control, immigration and income inequality. (Photo by Evan Vucci/Pool/Getty Images)

GOP Candidates Take Swings at Obama's SOTU

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Rubio, Cruz clash over proposed VAT tax

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NORTH CHARLESTON, SC - JANUARY 14: Republican presidential candidates (L-R) Donald Trump and Sen. Ted Cruz (R-TX) participate in the Fox Business Network Republican presidential debate at the North Charleston Coliseum and Performing Arts Center on January 14, 2016 in North Charleston, South Carolina. The sixth Republican debate is held in two parts, one main debate for the top seven candidates, and another for three other candidates lower in the current polls. (Photo by Scott Olson/Getty Images)

Trump to Cruz: You're a liability as a candidate

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Rubio to Cruz: We all saw you flip your vote

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Ted Cruz deflects NYT 'hit piece'

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Christie: State of the Union was story time with Obama

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Bush: Trump's ban makes it impossible to take out ISIS

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Cruz, Trump debate 'New York values'

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Sen. Rubio and Gov. Christie's heated exchange

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Trump answers Gov. Haley's 'angriest voices' remark

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Fiorina: We can't outsource leadership in Middle East

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Fiorina slams Trump, Clinton

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Huckabee: Obama keeps pushing ideas that never work

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Rick Santorm: Go Google me

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Rick Santorum to cadets: 'I will have your back'

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US Democratic presidential hopefuls (L-R) Bernie Sanders, Hillary Clinton and Martin O'Malley greet each other following the Democratic Presidential Debate hosted by ABC News at Saint Anselm College in Manchester, New Hampshire, on December 19, 2015.

ABC Democratic debate in two minutes

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Clinton: Trump 'is becoming ISIS' best recruiter'

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Clinton, Sanders, O'Malley talk spouses' roles

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Bernie Sanders: Corporate America 'ain't gonna like me'

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Clinton: Trump rhetoric encourages radicalization

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Bernie Sanders addresses data breach controversy

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Republican presidential candidate Ohio Governor John Kasich (L) speaks during the Republican Presidential Debate, hosted by CNN, at The Venetian Las Vegas on December 15, 2015 in Las Vegas, Nevada.

CNN Republican debate in 90 seconds

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Muslim voters react to GOP debate

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The gloomy America on display at the GOP debate

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Donald Trump: 'Oh, you're a tough guy Jeb'

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Bush to Trump: You can't insult your way to presidency

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Donald Trump responds to debate booing

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What’s at stake for 2016ers on debate night