WATCH: Sanders And Clinton Clash On Guns, Health Care In Democratic Debate

A feisty Bernie Sanders defended his positions on gun control and his newly released health care plan in Sunday night's Democratic presidential debate.

Just two weeks before the Iowa caucuses, the NBC News debate had a new urgency, with the Vermont senator closing the gap with Hillary Clinton in Iowa and New Hampshire. The two had mostly held their punches in their previous meetings, but much of their differences were laid bare during the face-off in Charleston, S.C.

"He has voted with the NRA and the gun lobby numerous times," Clinton charged, citing Sanders's past support for the Brady Bill, immunity for gun manufacturers and for the "Charleston loophole" that allowed Dylann Roof to allegedly get a gun to kill nine African-American churchgoers down the street at Mother Emanuel AME Church last June.

Sanders announced Saturday evening he would now back a bill in Congress that would repeal that immunity for manufacturers, but Clinton argued it wasn't enough.

"There's no other industry in America that was given a total pass," Clinton said.

Sanders argued that his opponent's argument was "disingenuous," pointing to his D- rating from the NRA, and said all along he had said he would "re-look" at the issue.

Former Maryland Gov. Martin O'Malley, still struggling to get momentum in the race and to jump into the skirmishes between the two frontrunners, argued he was the only one who had been consistent.

"I've never met a self-respecting hunter that needed an AR-15 to down a deer," O'Malley said.

Another flashpoint between Sanders and Clinton was on health care. Just two hours before Sunday's debate, the progressive favorite released his "Medicare-for-all" plan.

The universal health care proposal — which would have no co-pays or deductibles for patients — would be paid for with a new 2.2 percent health care premium, a 6.2 percent health care payroll tax paid for by employers, and an estate tax.

It would also be funded by a change in federal tax brackets — individuals making $250,000 to $500,000 a year would be taxed at a rate of 37 percent. Those earning $10 million or more a year would be taxed at 52 percent — but would only include about 13,000 households in the U.S.

Clinton attacked the plan though, saying it would "tear up" everything President Obama had accomplished with the Affordable Care Act, which should instead be improved upon.

"We finally have a path to universal health care. We have accomplished so much already. I do not want to see the Republicans repeal it and I do not want to start over again with another contentious debate," Clinton said.

Sanders shot back that her fears were "nonsense" and that something had to be done about the 29 million people who still did not have health care. He blamed big money and lobbyists for blocking bigger reforms, saying blocking money in politics would help fix the problem.

"A little more in taxes, do away with private insurance premiums, it's a pretty good deal," he argued, saying he didn't want to do away with the president's health care plan he had helped write.

Clinton shot back that Sanders has been inconsistent on what he wants though, asking if he supported "the plan you just introduced tonight or the plan you introduced nine times in the Congress."

In a city and a state that's faced recent racial strife — from the Charleston shooting to the killing of Walter Scott, an unarmed black man who was shot by a police officer — all the candidates also tackled the issues of policing and racial justice. The debate was hosted by the Congressional Black Caucus and came on the eve of Martin Luther King Day.

O'Malley defended his record as mayor of Baltimore, which has come under scrutiny in the wake of the death of Freddie Gray while in police custody last year.

Sanders said any death in police custody should automatically trigger a federal investigation.

"If a police officer breaks the law, like any public official, that person must be held accountable," he proposed.

But Sanders is losing African-American voters by a large margin according to polls, one big reason he's trailing Clinton in South Carolina where black voters dominate the primary. When pressed by moderator Lester Holt on his weakness, Sanders demurred, pointing to how far he had come from when he first entered the race.

"When the African-American community becomes familiar with my congressional record and with our agenda and with our views on the economy and criminal justice, just as the general population has become more supportive, so will the African-American community, so will the Latino community," Sanders said.

One demographic Sanders does have a commanding lead with is younger voters. In response to a YouTube question about how she'd work to win over millennials, Clinton pointed to her work on women's issues and civil rights. But she also seemed to tacitly acknowledge her opponent's strength with that bloc, saying she "respected" his support there.

Sanders frequently returned to one of his most salient attacks against Clinton — that she's too cozy with big businesses and Wall Street.

"I don't take money from the banks. I don't take personal speaking fees from Goldman Sachs," Sanders said, slamming Clinton for the $600,000 she took from the private corporate equity firm.

Clinton jabbed back that there's "no daylight" between herself and Sanders on financial reform and took issue with Sanders criticizing the president's leadership on banking reform.

"I'm going to defend Dodd-Frank and I'm going to defend President Obama," Clinton said.

While the first hour of the debate focused on domestic policy, the trio of Democrats did tackle foreign policy in the second half — a stark departure from Republican debates, where national security has dominated.

All three said they supported how President Obama was handling tensions with Syria and the rise of ISIS in the region but none said they supported sending U.S. ground forces to assist.

Sanders echoed calls before for bringing more allies into the fight against the terrorist organization.

"They have got to start putting some skin in the game, and not just ask the United States to do it," he said.

Sanders also said he was open to a "warm up" or relations with Iran as the U.S. did with Cuba this year, but cautioned not to move too quickly.

"Can I tell that we should open an embassy in Tehran tomorrow? No, I don't think we should," he said. "But I think the goal has go to be as we've done with Cuba, to move in warm relations with a very powerful and important country in this world."

Clinton also pointed to her experience as secretary of State, saying she was "proud" of the Iran nuclear agreement" and "was responsible for getting those sanctions imposed."

Copyright 2016 NPR. To see more, visit NPR.