Businessman Donald Trump watches U.S. Sen. Ted Cruz speak Tuesday, December 15, during a Republican presidential debate in Las Vegas.
An overhead view of the stage at the Venetian hotel and casino.
Trump answers a question at the debate. During the event, the GOP front-runner said it was "very unprofessional" and "very sad" that so many questions directed at other candidates were about him.
Cruz, the junior U.S. senator from Texas, has been gaining in the polls recently. "We need a President who understands the first obligation of the commander-in-chief is to keep America safe," he said in his opening remarks. "If I am elected President, we will hunt down and kill the terrorists. We will utterly destroy ISIS."
New Jersey Gov. Chris Christie, center, makes a point between former Florida Gov. Jeb Bush, left, and U.S. Sen. Rand Paul. "I'm a former federal prosecutor," Christie said during the debate. "I've fought terrorists and won, and when we get back in the White House we will fight terrorists and win again and America will be safe." Much of Tuesday night's debates focused on national security and the ISIS terror threat.
Candidate Ben Carson speaks during the debate. "As a pediatric neurosurgeon, I frequently faced life-and-death situations and had to come up with the right diagnosis, the right plan, and execute that plan frequently with other colleagues," Carson said. "Right now, the United States of America is the patient. And the patient is in critical condition and will not be cured by political correctness and will not be cured by timidity."
Businesswoman Carly Fiorina, left, responds to a question from debate moderator Wolf Blitzer. In her opening remarks, Fiorina said: "I have been tested. I have beaten breast cancer. I have buried a child. I started as a secretary. I fought my way to the top of corporate America while being called every B-word in the book. I fought my way into this election and on to this debate stage while all the political insiders and the pundits told me it couldn't be done."
Bush makes a point as Cruz looks on during the debate. Bush clashed with Trump often during the debate, at one point calling him a "chaos candidate."
U.S. Sen. Marco Rubio answers a question during the debate. "Today you have millions of Americans that feel left out and out of place in their own country, struggling to live paycheck to paycheck, called bigots because they hold on to traditional values," the junior U.S. senator from Florida said. "And around the world, America's influence has declined while this president has destroyed our military, our allies no longer trust us, and our adversaries no longer respect us. And that is why this election is so important."
Carson and Trump share a laugh on stage.
Ohio Gov. John Kasich speaks during the debate. "When we think about our country and the big issues that we face in this country -- creating jobs, making sure people can keep their jobs, the need for rising wages, whether our children when they graduate from college can find a job, protecting the homeland, destroying ISIS, rebuilding defense -- these are all the things that we need to focus on," Kasich said. "But we'll never get there if we're divided. We'll never get there if Republicans and Democrats just fight with one another."
Paul waves as he takes the stage before the start of the debate. "I think we defeat terrorism by showing them that we do not fear them," said the junior U.S. senator from Kentucky. "I think if we ban certain religions, if we censor the Internet, I think that at that point the terrorists will have won."
The candidates put their hands over the hearts during the national anthem.
A wide shot of the Venetian theater.
Four Republican presidential candidates take the stage for the "undercard" debate featuring lower-polling candidates. From left are former New York Gov. George Pataki, former Arkansas Gov. Mike Huckabee, former U.S. Sen. Rick Santorum and U.S. Sen. Lindsey Graham.
Graham has served South Carolina in Congress since 1995. He continued his tough talk on the threat of terrorism. "If I'm President of the United States, and you join ISIL, you are going to get killed or captured," he said. "And the last thing you are going to hear if I'm President is, 'You've got a right to remain silent.' "
Huckabee responds to a question. "We've lost confidence in our government," Huckabee said during the first debate. "And when Americans lose confidence in their government, we're in a dangerous place. We're in danger because we have an enemy that is out to kill us, and we have a government that we don't trust any more. This election is about going back to having a government we can trust with leaders who have the courage and conviction to actually lead and not follow."
Santorum, who served Pennsylvania in the U.S. Senate, also ran for President in 2012. "This is an important time in our country's history," he said in his opening remarks. "We have entered World War III. World War III has begun, and we have a leader who refuses to identify it and be truthful to the American people to the stakes that are involved, in part, because his policies have led us here."
Former Alaska Gov. Sarah Palin -- Sen. John McCain's running mate in 2008 -- watches the debate from the audience.
Pataki was New York governor from 1995 to 2006. "Our party needs to nominate a strong leader who will unite us as Republicans, but more importantly, unite us as Americans," he said at the beginning of the first debate.