Washington (CNN) Bernie Sanders is defending his record on the one issue on where some liberal members of his party consider him too moderate: guns.

Biden greets Sanders with an elbow bump before the start of a debate in Washington in March 2020. They went with an elbow bump instead of a handshake because of the coronavirus pandemic.

Biden greets Sanders with an elbow bump before the start of a debate in Washington in March 2020. They went with an elbow bump instead of a handshake because of the coronavirus pandemic.

Sanders speaks to reporters in Burlington, Vermont, a day after Super Tuesday II. Sanders said it "was not a good night for our campaign from a delegate point of view" but that he looked forward to staying in the race and taking on Joe Biden in an upcoming debate.

A triumphant Sanders raises his fist in San Antonio after he was projected to win the Nevada caucuses.

Sanders laughs during a primary-night rally in Manchester, New Hampshire, in February 2020. Sanders won the primary, just as he did in 2016.

In a tense and dramatic exchange moments after a Democratic debate, Warren accused Sanders of calling her a liar on national television. Sanders responded that it was Warren who called him a liar. Earlier in the debate, the two disagreed on whether Sanders told Warren, during a private dinner in 2018, that he didn't believe a woman could win the presidency.

US Rep. Alexandria Ocasio-Cortez introduces Sanders at a New York rally after endorsing him for president in October 2019.

US Rep. Alexandria Ocasio-Cortez introduces Sanders at a New York rally after endorsing him for president in October 2019.

Sanders campaigns at the University of New Hampshire in September 2019. A few days later, he took himself off the campaign trail after doctors treated a blockage in one of his arteries. Sanders suffered a heart attack, his campaign confirmed.

Sanders grabs the hand of US Sen. Elizabeth Warren during the Democratic debates in Detroit in July 2019.

Sanders grabs the hand of US Sen. Elizabeth Warren during the Democratic debates in Detroit in July 2019.

Sanders speaks next to former Vice President Joe Biden at the first Democratic debates in June 2019.

Sanders speaks next to former Vice President Joe Biden at the first Democratic debates in June 2019.

Sanders looks at his notes as he watches President Trump deliver the State of the Union address in February 2019. That month, Sanders announced that he would be running for president again.

Sanders looks at his notes as he watches President Trump deliver the State of the Union address in February 2019. That month, Sanders announced that he would be running for president again.

Sanders brings a giant printout of one of Donald Trump's tweets to a Senate debate in January 2017. In the tweet, Trump had promised not to cut Social Security, Medicare and Medicaid.

Sanders speaks at a rally in Santa Monica, California, in June 2016. He pledged to stay in the Democratic race even though Clinton secured the delegates she needed to become the presumptive nominee.

Sanders speaks at a rally in Santa Monica, California, in June 2016. He pledged to stay in the Democratic race even though Clinton secured the delegates she needed to become the presumptive nominee.

Sanders speaks at a campaign rally in Ann Arbor, Michigan, in March 2016. He won the state's primary the next day, an upset that delivered a sharp blow to Clinton's hopes of quickly securing the nomination.

Sanders and his wife, Jane, wave to the crowd during a primary night rally in Concord, New Hampshire, in February 2016. Sanders defeated Clinton in the New Hampshire primary with 60% of the vote, becoming the first Jewish candidate to win a presidential primary.

Comedian Larry David and Sanders appear together on "Saturday Night Live" in February 2016. David had played Sanders in a series of sketches throughout the campaign season.

Sanders sits with rapper and activist Killer Mike at the Busy Bee Cafe in Atlanta in November 2015. That evening, Killer Mike introduced Sanders at a campaign event in the city. "I'm talking about a revolutionary," the rapper told supporters. "In my heart of hearts, I truly believe that Sen. Bernie Sanders is the right man to lead this country."

Sanders embraces Remaz Abdelgader, a Muslim student, during an October 2015 event at George Mason University in Fairfax, Virginia. Asked what he would do about Islamophobia in the United States, Sanders said he was determined to fight racism and "build a nation in which we all stand together as one people."

Sanders embraces Remaz Abdelgader, a Muslim student, during an October 2015 event at George Mason University in Fairfax, Virginia. Asked what he would do about Islamophobia in the United States, Sanders said he was determined to fight racism and "build a nation in which we all stand together as one people."

Seconds after Sanders took the stage for a campaign rally in August 2015, a dozen protesters from Seattle's Black Lives Matter chapter jumped barricades and grabbed the microphone from the senator. Holding a banner that said "Smash Racism," two of the protesters -- Marissa Johnson, left, and Mara Jacqueline Willaford -- began to address the crowd.

In July 2015, two months after announcing he would be seeking the Democratic Party's nomination for President, Sanders spoke to nearly 10,000 supporters in Madison, Wisconsin. "Tonight we have made a little bit of history," he said. "You may know that some 25 candidates are running for President of the United States, but tonight we have more people at a meeting for a candidate for President of the United States than any other candidate has."

In March 2015, Sanders speaks in front of letters and petitions asking Congress to reject proposed cuts to Social Security and Medicare.

In March 2015, Sanders speaks in front of letters and petitions asking Congress to reject proposed cuts to Social Security and Medicare.

Sanders and US Rep. Jeff Miller, chairman of the House Committee on Veterans' Affairs, walk to a news conference on Capitol Hill in 2014. Sanders was chairman of the Senate Committee on Veterans' Affairs.

Sanders and US Rep. Jeff Miller, chairman of the House Committee on Veterans' Affairs, walk to a news conference on Capitol Hill in 2014. Sanders was chairman of the Senate Committee on Veterans' Affairs.

Sanders speaks to reporters in 2010 about the Obama administration's push to extend Bush-era tax cuts. Three days later, Sanders held a filibuster against the reinstatement of the tax cuts. His speech, which lasted more than eight hours, was published in book form in 2011. It is called "The Speech: A Historic Filibuster on Corporate Greed and the Decline of Our Middle Class."

Sanders speaks to reporters in 2010 about the Obama administration's push to extend Bush-era tax cuts. Three days later, Sanders held a filibuster against the reinstatement of the tax cuts. His speech, which lasted more than eight hours, was published in book form in 2011. It is called "The Speech: A Historic Filibuster on Corporate Greed and the Decline of Our Middle Class."

Sanders chats with Dr. John Matthew, director of The Health Center in Plainfield, Vermont, in May 2007. Sanders was in Plainfield to celebrate a new source of federal funding for The Health Center.

Sanders chats with Dr. John Matthew, director of The Health Center in Plainfield, Vermont, in May 2007. Sanders was in Plainfield to celebrate a new source of federal funding for The Health Center.

Sanders takes part in a swearing-in ceremony at the US Capitol in January 2007. He won his Senate seat with 65% of the vote.

Sanders takes part in a swearing-in ceremony at the US Capitol in January 2007. He won his Senate seat with 65% of the vote.

Sanders sits next to President Bill Clinton in 1993 before the Congressional Progressive Caucus held a meeting at the White House. Sanders co-founded the caucus in 1991 and served as its first chairman.

Sanders sits next to President Bill Clinton in 1993 before the Congressional Progressive Caucus held a meeting at the White House. Sanders co-founded the caucus in 1991 and served as its first chairman.

In 1990, Sanders defeated US Rep. Peter Smith in the race for Vermont's lone House seat. He won by 16 percentage points.

In 1990, Sanders defeated US Rep. Peter Smith in the race for Vermont's lone House seat. He won by 16 percentage points.

Sanders reads mail at his campaign office in Burlington in 1990. He was running for the US House of Representatives after an unsuccessful bid in 1988.

Sanders reads mail at his campaign office in Burlington in 1990. He was running for the US House of Representatives after an unsuccessful bid in 1988.

In 1987, Sanders and a group of Vermont musicians recorded a spoken-word folk album. "We Shall Overcome" was first released as a cassette that sold about 600 copies. When Sanders entered the US presidential race in 2015, the album surged in online sales. But at a CNN town hall, Sanders said, "It's the worst album ever recorded."

Sanders, right, tosses a baseball before a minor-league game in Vermont in 1984. US Sen. Patrick Leahy, center, was also on hand.

Sanders, right, tosses a baseball before a minor-league game in Vermont in 1984. US Sen. Patrick Leahy, center, was also on hand.

Sanders takes the oath of office to become the mayor of Burlington, Vermont, in 1981. He ran as an independent and won the race by 10 votes.

Sanders takes the oath of office to become the mayor of Burlington, Vermont, in 1981. He ran as an independent and won the race by 10 votes.

Sanders, right, leads a sit-in organized by the Congress of Racial Equality in 1962. The demonstration was staged to oppose housing segregation at the University of Chicago. It was Chicago's first civil rights sit-in.

Sanders, right, leads a sit-in organized by the Congress of Racial Equality in 1962. The demonstration was staged to oppose housing segregation at the University of Chicago. It was Chicago's first civil rights sit-in.

US Sen. Bernie Sanders speaks at a campaign rally in Chicago in March 2019. Sanders, an independent from Vermont, is the longest-serving independent in the history of Congress.

US Sen. Bernie Sanders speaks at a campaign rally in Chicago in March 2019. Sanders, an independent from Vermont, is the longest-serving independent in the history of Congress.

The Vermont senator and his Democratic liberal base are simpatico on nearly every policy area -- but gun control has long been an exception. Hailing from a rural state with few gun restrictions, Sanders has sought a middle ground.

It's an issue all but certain to come up Tuesday night in Las Vegas, when the Democratic presidential field meets for its first debate following three recent campus shootings.

In an interview with NBC's Chuck Todd set to air Sunday on "Meet the Press," Sanders said that in Washington, lawmakers "keep shouting at each other, which is what's been going on here for 20 years" and it "ain't going nowhere."

He said he sees an opening to advance "common sense gun reform" as well as "a revolution in mental health."

"When the vast majority of the American people say it's pretty crazy that guns are falling into the hands of people who are either criminals or mentally ill and they're shooting up kids -- yeah, I think we can build on that," he said.

Sanders' record on gun control has angered both anti-gun groups and the National Rifle Association.

He has supported universal background checks for gun buyers, a ban on assault weapons and the closure of the so-called gun show loophole that allows sales to take place without background checks.

But he has also voted to allow guns in national parks and on Amtrak trains, opposed a five-day waiting period for gun purchases and backed for a 2005 measure that shielded gun manufacturers from liability in lawsuits over shootings.

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Sanders was pressed Sunday on that 2005 vote -- one that's drawn new criticism from liberal groups during his presidential bid. He said he's open to "another look" at the issue.

"That was a complicated vote and I'm willing to see changes in that provision," Sanders said. "Here's the reason I voted the way I voted: If you are a gun shop owner in Vermont and you sell somebody a gun and that person flips out and then kills somebody, I don't think it's really fair to hold that person responsible, the gun shop owner.

"On the other hand, where there is a problem is there is evidence that manufacturers, gun manufacturers, do know that they're selling a whole lot of guns in an area that really should not be buying that many guns. That many of those guns are going to other areas, probably for criminal purposes. So can we take another look at that liability issue? Yes."

The vote to protect gun manufacturers from lawsuits could hurt Sanders the most. In the past he has voted to make it easier to sue airlines for crashes over water, machine tool makers for injuries that happen after 18 years of use, restaurants over mislabeled food that contributed to weight gain and more.

It's not clear how many of Sanders' supporters would be turned off by his gun votes. Russell Mendell, a 30-year-old Democratic voter in Boulder, Colorado, said he won't hold those votes against him.

"I think you can go back on any candidate who has been around for 30 years and find some issues that you don't agree on," he said. "I agree with Bernie Sanders on about 95 to 96 percent of things. I am not going to agree with any candidate all the time."

Sanders also talked guns at a rally in front of 13,000 people Friday night in Tucson, Arizona.

"It goes without saying that our condolences go to the families of those who were killed and our hearts and prayers go out for a full recovery for those who were wounded," Sanders said after mentioning shootings at Texas Southern University and Northern Arizona University. "But we also know that we are tired of condolences and we are tired of just prayers."

Sanders argued that while the issue of gun control is "not going to be solved easily," that "does not mean we do not address it and do the best we can."

"Yes there are disagreement on how we go forward in terms of gun safety," Sanders said. "But I think the vast majority of the American people want us to move forward in sensible ways which keep guns out of the hands of people who should not have them."