Best Lines of the Fourth Democratic Debate The first Democratic debate of 2016 kicked off in South Carolina Sunday.

 -- The first Democratic debate of 2016 kicked off in Charleston, South Carolina.

Hillary Clinton, Bernie Sanders and Martin O’Malley duked it out Sunday night in a debate hosted by NBC News.

There was no shortage of heated exchanges in what is becoming an increasingly contentious campaign, particularly between Sanders and Clinton. Sanders, for example, was asked to address his comments on Bill Clinton’s sexual indiscretions during his presidency, to which he repeated he is running against Secretary Clinton.

“I'm going to debate Secretary Clinton, Governor O'Malley on the issues facing the American people, not Bill Clinton's personal behavior.”

Here are the best lines of the debate:

On Gun Laws

BERNIE SANDERS: “Well, I think Secretary Clinton knows what she says is disingenuous. I have a D-minus voting record from the NRA.”

Democratic front-runner, HILLARY CLINTON responded: “I have made it clear, based on Senator Sanders’ own record that he has voted with the NRA, with the gun lobby numerous times,” adding, “Now, I am pleased to hear that Senator Sanders has reversed his position on immunity, and I look forward to him joining with those members of Congress who have already introduced legislation.”

MARTIN O’MALLEY: “I've never met a self-respecting deer hunter that needed an AR-15 to down a deer.”

On Race and the Criminal Justice System

HILLARY CLINTON: “One out of three African-American men may well end up going to prison. That's the statistic. I want people here to think what we would be doing if it was one out of three white men.”

BERNIE SANDERS: “We have a criminal justice system which is broken. Who in America are satisfied that we have more people in jail than any other country on Earth, including China? Disproportionately African-American and Latino. Who is satisfied that 51 percent of African-American young people are either unemployed or underemployed. Who is satisfied that millions of people have police records for possessing marijuana when the CEOs of Wall Street companies who destroyed our economy have no police record.

“If a police officer breaks the law, like any public official, that officer must be held accountable,” Sanders added.

At the end of the debate Clinton expressed her outrage at the water contamination crisis in Flint Michigan.

“We've had a city in the united States of America where the population, which is poor in many ways, and majority African American has been drinking and bathing in lead-contaminated water,” she said. "I'll tell you what if the kids in a rich suburb of Detroit had been drinking contaminated water and being bathed in it, there would have been action.”

On Polls

BERNIE SANDERS: “Secretary Clinton well knows, when this campaign began, she was 50 points ahead of me. We were all of 3 percentage points. Guess what? In Iowa, New Hampshire, the race is very, very close. In terms of polling, guess what, we are running ahead of Secretary Clinton in terms of taking on my good friend, Donald Trump.”

On Drug Abuse

HILLARY CLINTON: “We have to move away from treating the use of drugs a as crime and, instead, move it to where it belongs, as a health issue. And we need to divert more people from the criminal justice system into drug courts, into treatment, and recovery.”

BERNIE SANDERS: “When we talk about addiction being a disease, the secretary is right, what that means is we need a revolution in this country in terms of mental health treatment.”

On Obamacare

HILLARY CLINTON: ”Here's what I believe, the Democratic Party and the United States has worked since Harry Truman to get the Affordable Care Act passed.”

BERNIE SANDERS fired back, saying, “The truth is, that Franklin Delano Roosevelt, Harry Truman, do you know what they believed in, they believed that health care should be available to all of our people.”

The exchange between the two didn’t end there. In response to Sanders’ recently unveiled health plan, Clinton scoffed, “I'm not sure whether we're talking about the plan you just introduced tonight or we're talking about the plan you introduced nine times in the Congress, but the fact is, we have the Affordable Care Act.”

Just two hours before the fourth Democratic debate kicked off, presidential hopeful Bernie Sanders released a proposal to create a new single-payer health care system in the United States.

Clinton continued to rebuke Sanders for the proposal, defending the Affordable Care Act as “one of the greatest accomplishments of president Obama, of the democratic party, and of our country.”

Sanders demurred, saying “no one is tearing [the Affordable Care Act] up. We're going to go forward.”

On Breaking Up the Big Banks

When asked by moderators how his plan to break up the big banks would differ from his Democratic rival Hillary Clinton, Sanders’ argued, “Well, the first difference is I don't take money from big banks. I don't get personal speaking fees from Goldman Sachs.”

HILLARY CLINTON responded by criticizing Sanders for his distance from President Obama.

“So I'm going to defend Dodd Frank, and I'm going to defend President Obama for taking on Wall Street, taking on the financial industry, and getting results,” she said.

SANDERS retorted, “I have doubts when people receive huge amounts of money from Wall Street. I am very proud, I do not have a super PAC. I do not want Wall Street's money. I'll rely on the middle class and working families.”

MARTIN O’MALLEY: “Look, if a bank robber robs a bank and all you do is slap him on the wrist, he's just going to rob banks again. The same thing is true with people in suits.”

On Climate Change

SANDERS took aim at his GOP opponents: “It is beyond my comprehension how we can elect a president of the United States, somebody like Trump who believes that climate change is a hoax, invented by the Chinese.”

Back in November 2012, GOP front-runner Donald Trump took to Twitter to share his theory on global warming. “The concept of global warming was created by and for the Chinese in order to make U.S. manufacturing non-competitive,” Trump wrote.

On Russian President Vladimir Putin

When asked the nature of her relationship with Russian President Vladimir Putin, HILLARY CLINTON responded, “Well my relationship with him, it's -- it's, it's interesting.”

“I think it’s one, I think of respect,” she said. “I know that he's someone that you have to continuingly stand up to because, like many bullies, he is somebody who will take as much as he possibly can unless you do.”

On Privacy vs. Security

MARTIN O’ MALLEY: “I believe whether it's a back door or front door, that the American principle of law should still hold that our federal government should have to get a warrant. Whether they want to come through the back door or your front door.”

On Bill Clinton

During the last Democratic debate, HILLARY CLINTON said she would turn to her husband "for advice and, in particular, how we're going to get the economy working again for everybody.” Tonight, she was asked to clarify whether this would be a “kitchen table role on economics” or a “real policy role.”

“Well, it'll start at the kitchen table, we'll see how it goes from there,” she quipped.

BERNIE SANDERS, meanwhile, defended his criticisms of the former president’s indiscretions.

“I was asked a question,” Sanders said, “and that question, annoys me. I cannot walk down the street, Secretary Clinton knows that, without being told how much I have to attack Secretary Clinton. To want to get me on the front page of the paper, I make a vicious attack.”

Sanders made the harsh critique while campaigning in Iowa, when he was asked whether his main opponent, Hillary Clinton, was qualified to be president.

“My question to you is: Isn’t one of the qualifications of being president some sort of moral authority?” the man asked, noting that Clinton had “a known affair in the Oval with an intern” -- a reference to his involvement with Monica Lewinsky.

“I hear what you’re saying,” Sanders interjected. “Look Hillary Clinton is not Bill Clinton. What Bill Clinton did, I think we can all acknowledge was totally, totally disgraceful and unacceptable, but I am running against Hillary Clinton. I am not running against Bill Clinton, though I understand he has been in Iowa recently.”

Sanders reiterated he is running against Hillary and not Bill Clinton tonight, “Yes, his behavior was deplorable, have a said a word? No, I have not. I'm going to debate Secretary Clinton, Governor O'Malley on the issues facing the American people, not Bill Clinton's personal behavior.”