Photos:: Republican presidential candidates debate

Sen. Ted Cruz answers a question as Ben Carson looks on during the Republican presidential debate in Des Moines.

Chris Christie makes a point as Rand Paul listens.

Republican presidential candidate Donald Trump speaks at an event at Drake University in Des Moines, which he attended instead of the debate elsewhere in town.

Donald Trump laughs as Rick Santorum jokes about not wanting to be photographed in front of a Trump campaign sign during their appearance at Drake University.

Members of the audience show support during a Donald Trump event at Drake University.

Thursday’s GOP debate is the last before the presidential voting begins next week in Iowa.

Jeb Bush makes a point as Marco Rubio listens during the debate.

Rand Paul responds to a question.

Ted Cruz, left, and Marco Rubio.

From left, Rand Paul, Chris Christie, Ben Carson, Ted Cruz, Marco Rubio, Jeb Bush and John Kasich share the stage before the debate.

Ben Carson, left, Ted Cruz, Marco Rubio and Jeb Bush take the stage for the debate.

FOX News moderators Chris Wallace, left, Megyn Kelly and Bret Baier before the start of the main debate.

Rick Santorum, left, argues a point as Carly Fiorina, Mike Huckabee and Jim Gilmore listen during the GOP undercard debate in Des Moines.

Carly Fiorina at the Republican undercard debate in Des Moines.

Mike Huckabee at the Republican undercard debate in Des Moines.

Jim Gilmore speaks in Des Moines at the undercard debate for Republican presidential candidates.

Rick Santorum argues a point during a Republican presidential primary debate in Des Moines.

Republican presidential candidates Rick Santorum, Carly Fiorina, Mike Huckabee and Jim Gilmore, from left, before the Fox News-Google GOP undercard debate at the Iowa Events Center in Des Moines.