Photos:: Republican presidential debate

Donald Trump, left, and Ted Cruz.

GOP candidate John Kasich, right, speaks as rival Ted Cruz looks on.

Republican presidential candidate Ben Carson makes a point in the debate.

Republican presidential candidate Marco Rubio.

Marco Rubio, left, and Donald Trump in the Republican presidential candidate debate in Houston.

Donald Trump makes a point in the debate.

Donald Trump, left, Ted Cruz and John Kasich in the Republican debate.

Ohio Gov. John Kasich.

Marco Rubio and Ted Cruz are seen on a screen in the media room at the Republican presidential debate.

Republican presidential candidate, Sen. Ted Cruz, R-Texas, looks on during a Republican presidential primary debate at The University of Houston.

Republican presidential candidates, from left, Ben Carson, Marco Rubio, Donald Trump, Ted Cruz and John Kasich.

The candidates listen to the national anthem.

Marco Rubio, Donald Trump and Ted Cruz.

Ben Carson meets with members of the news media before the debate.

Texas Gov. Greg Abbott arrives at the Houston debate.

Former President George H.W. Bush and his wife, Barbara, attend the debate.

The main stage before the debate.