6:57 p.m. Closing statements. Santorum says there should be someone who takes on the establishment and takes on Hillary Clinton.
"I know I'm out of time, but I'm going to take some of Rand Paul's time for a second," Santorum said. Paul chose not to participate in the undercard debate.
Huckabee said he would protect moral values in the U.S.
Fiorina said, "You cannot wait to see the debate between me and Hillary Clinton."
6:47 p.m. Huckabee says the reason why people have a hard time getting ahead because people of the current tax code.
"It's why I really believe to do something bold," he said, pushing for a "fair tax."
6:34 p.m. Responding to a question about the vulnerabilities of the visa waiver program, Huckabee blasted President Obama for defending Muslims in his final State of the Union address. He said American Jews are targeted much more than Muslims.
6:27 p.m. Question is about President Obama's new executive actions on guns.
Huckabee declares, "There is no gun show loophole," and that none of the president's proposals would have stopped the shootings in San Bernardino, Aurora, etc.
"Of course we want to stop gun violence," Huckabee said, but added that the common thread is that most shootings have occurred in gun-free zones.
6:26 p.m. Santorum says it would be "dicey" if the government required Facebook and Twitter to help fight terrorism. Instead, he said the government should be developing that capability itself.
Fiorina, the former CEO of Hewlett Packard, said she disagrees with Santorum. She said the government should ask the private sector to get involved.
6:17 p.m. Moderators bring up the sexual assaults in Germany by asylum seekers during New Year's Eve. Fiorina responds by saying the U.S. "should stop allowing refugees into this country" because the administration cannot properly vet them.
Fiorina said Trump has a "bromance" with Russian President Vladimir Putin and said Russia is an enemy of the U.S.
6:09 p.m. Candidates are asked how they view America's role in the world. Fiorina slams President Obama and Hillary Clinton and says they "refuse to lead."
"We have refused to respond to every provocation," Fiorina said.
Santorum is asked how he would navigate handling the Iran deal as president and staying close to U.S. allies in the region. The former Pennsylvania senator says on the first day of his presidency the deal would be "torn up" and Iran has "already torn it up" and "violated" the nuclear deal.
Huckabee is asked what his solution is to the growing conflict in Afghanistan, which he then called "the land of the Flintstones." He said that the U.S. should only be in Afghanistan if there is a concerted effort to defeat radical Islamists.
6:03 p.m. First question to the candidates is what they think about the state of the U.S. economy.
Fiorina first jabs Hillary Clinton on a completely unrelated topic.
"Unlike another woman in this race, I actually love spending time with my husband," Fiorina says of the Democratic presidential candidate.
She goes onto say, "The state of our economy is not strong."
Huckabee says there are still a lot of people hurting today. Santorum says 2 million manufacturing jobs have left the U.S. because of President Obama and his mission to reduce global climate change.
6:00 p.m. The second tier of Republican candidates face off in the "happy hour" debate on Fox Business in South Carolina. They are Carly Fiorina, Mike Huckabee and Rick Santorum.
Sen. Rand Paul, R-Kentucky, has decided to boycott the lower-tier debate. It marks the first time Paul was ineligible for the main debate stage and said earlier this week that he wouldn't participate in anything that's not first tier.
Since the last GOP debate in mid-December, Sen. Lindsey Graham, R-South Carolina, and former New York Gov. George Pataki have suspended their presidential campaigns.
Moderators Trish Regan and Sandra Smith are expected to grill candidates on economic, domestic and international policy issues.
The main debate featuring the top seven candidates begins at 9 p.m. ET.