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LAS VEGAS, NV - OCTOBER 13:  Democratic presidential candidates U.S. Sen. Bernie Sanders (I-VT) (L) and Hillary Clinton shake hands at the end of a presidential debate sponsored by CNN and Facebook at Wynn Las Vegas on October 13, 2015 in Las Vegas, Nevada. Five Democratic presidential candidates are participating in the party's first presidential debate.  (Photo by Joe Raedle/Getty Images)
LAS VEGAS, NV - OCTOBER 13:  Democratic presidential candidates U.S. Sen. Bernie Sanders (I-VT) (L) and Hillary Clinton shake hands at the end of a presidential debate sponsored by CNN and Facebook at Wynn Las Vegas on October 13, 2015 in Las Vegas, Nevada. Five Democratic presidential candidates are participating in the party's first presidential debate.  (Photo by Joe Raedle/Getty Images)

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Tensions growing between Democratic front-runners

As the Democratic race heats up, front-runners Hillary Clinton and Bernie Sanders are going on the offensive. CNN's Brianna Keilar has the story.

Tensions growing between Democratic front-runners

As the Democratic race heats up, front-runners Hillary Clinton and Bernie Sanders are going on the offensive. CNN's Brianna Keilar has the story.