Two of the candidates who appeared during the prime-time debate, Ben Carson and Rand Paul, are medical doctors. Carson is a brain surgeon, and Paul is an eye doctor. The moderators mainly asked Carson about foreign policy and Paul mostly about non-health issues, such as his views on Israel and on data privacy.

For details about what Trump, Kasich and other candidates said, read on.

Donald Trump

Brett Baier asked Trump to discuss reports that, 15 years ago, Trump called himself "a liberal on health care" and promoted a shift to a Canadian-style single-payer system.

"Why were you for that then and why aren't you for it now?" Baier asked.

Trump said that, in the past, he supported a shift to a single-payer system because that approach has worked in Canada and in Scotland. In the United States, "it could have worked in a different age, which is the age you're talking about here," Trump said.

Trump said that, today, he'd like to see a "private system without the artificial lines around every state."

Trump, a real estate developer, said he has a big company with thousands of employees in multiple states. "If I'm in negotiating in New York or in New Jersey or in California, I have, like, one bidder," he said. "Nobody can bid. You know why? Because the insurance companies are making a fortune because they have control over the politicians. Of course, with the exception of the politicians on this stage. But they have total control over the politicians. They're making a fortune."

Getting rid of the artificial lines separating each state's insurance market from the others would leave the market with great plans, Trump said.

"And then we have to take care of the people that can't take care of themselves," Trump said. "I'll do that through a different system."

At another point, Trump said the country has to end PPACA.

John Kasich

Moderator Megyn Kelly asked Kasich about his decision to take PPACA Medicaid expansion money, and reports that Medicaid expansion has cost $1.4 billion more in the state than originally expected.

"You defended your Medicaid expansion by invoking God, saying to skeptics that, when they arrive in heaven, St. Peter isn't going to ask them how small they've kept government, but what they've done for the poor," Kelly said. "Why should Republican voters, who generally want to shrink government, believe that you won't use your St. Peter rationale to expand every government program?" she asked. 

Kasich told Kelly that President Reagan expanded Medicaid three or four times.

Expanding Medicaid gave Ohio the money to treat the many state prison inmates who are mentally ill or addicted to drugs, Kasich said.

"We now treat them in the prisons and release them," Kasich said. "The recidivism rate is 10 percent. So, we're treating them and getting them on their feet."

Medicaid expansion also helps keep the working poor from depending on hospital emergency rooms for routine care, Kasich said.

3. The other candidates

During the early debate, Lindsey Graham and Bobby Jindal emphasized that they will be serious about repealing PPACA.

Scott Walker, Marco Rubio, Rand Paul and Jeb Bush made a point of saying they would repeal or otherwise get rid of PPACA. 

Several candidates took note of Trump's past expressions of support for a single-payer health care system.

"News flash," Paul said, while Trump was answering questions. "The Republican Party's been fighting against a single-payer system for a decade. I think you're on the wrong side of this if you're still arguing for a single-payer system."

"I don't think you heard me," Trump said. "You're having a hard time tonight."

During the early debate, Rick Perry said Trump's views on the issue suggest that he's relying on his celebrity status, not his conservatism.

"How can you run for the Republican nomination and be for single-payer health care?" Perry asked. "I mean, I ask that with all due respect."

Carly Fiorina reacted to Trump's comments that he has changed his mind on health care.

"Since he has changed his mind on amnesty, on health care and on abortion, I would just ask, what are the principles by which he will govern?" Fiorina asked.