Joe Raedle/Getty Images

MANCHESTER, NH - FEBRUARY 06: Republican presidential candidate New Jersey Governor Chris Christie participates in the Republican presidential debate at St. Anselm College February 6, 2016 in Manchester, New Hampshire. Sponsored by ABC News, the Independent Journal Review and Google, this is the final televised debate before voters go to the polls for the New Hampshire primary on February 9. (Photo by Joe Raedle/Getty Images)

Now playing

02:14

Rubio, Christie exchange blows early

Edward M. Pio Roda/CNN

CNN Republican Debate at the University of Miami.

Now playing

02:32

Donald Trump pressed for specifics of his worldview

CNN

Now playing

00:59

Ted Cruz: Trump hand-raising pledge 'exactly backwards'

Edward M. Pio Roda/CNN

CNN Republican Debate at the University of Miami.

Now playing

01:45

Donald Trump on rally violence: It's not me

CNN

Now playing

01:54

Should the candidate with the most delegates win?

Edward M. Pio Roda/CNN

CNN Republican Debate at the University of Miami.

Now playing

01:26

Does it matter how the world sees the U.S.?

John Kasich post republican debate Miami intv serfaty ac_00002110.jpg

Now playing

01:07

John Kasich: I'm doing really, really well

Edward M. Pio Roda/CNN

CNN Republican Debate at the University of Miami.

Now playing

01:30

Marco Rubio: 'The climate is always changing'

RHONA WISE/AFP/Getty Images

Republican Presidential candidate Donald Trump speaks during the CNN Debate in Miami on March 10, 2016.

Now playing

01:33

Reality check: Trump's ISIS oil claims misleading?

Edward M. Pio Roda/CNN

CNN Republican Debate at the University of Miami.

Now playing

02:35

Donald Trump, Marco Rubio spar over Cuba

CNN

Now playing

01:09

Donald Trump: 'Elegant debate' that we needed

Joe Raedle/Getty Images/File

HOUSTON, TX - FEBRUARY 24: Republican presidential candidate U.S. Sen. Marco Rubio (R-FL) speaks during a campaign rally at the Marriott South at Hobby Airport on February 24, 2016 in Houston, Texas. The process to select the next Democratic and Republican Presidential candidates continues. (Photo by Joe Raedle/Getty Images)

Now playing