One issue is almost guaranteed to be a central part of the first Democratic debate

With two hours of questions, and only five candidates onstage, the Democratic presidential candidates have spent the past few weeks preparing to field questions on almost every major political subject imaginable.

But one issue in particular suddenly looms large over the first Democratic presidential debate: gun control.

A spate of deadly mass shootings, including one less than two weeks ago in Oregon, has consistently thrust gun control back into the public consciousness. The issue has become a near-constant presence in the news media.

Since the Sandy Hook Elementary School massacre in 2012 that left 20 children and six others dead, Democrats have become emboldened in their support for stricter gun laws. Republicans have blocked various attempts to place more restrictions on guns. But the issue has reached a fever pitch during the campaign, as a number of high-profile shootings have littered the country.

“I worked here in 2012, and I know how hard it was to get the candidates to address gun violence,” Erika Soto Lamb, the communications director for the group Everytown for Gun Safety, told Business Insider earlier this year. “The candidates have been talking about guns far more than they did then.”

Democratic presidential front-runner Hillary Clinton has released a sweeping plan to combat gun violence. The team of one of her top rivals, former Maryland Gov. Martin O’Malley, is constantly emphasising his record on the issue.

And advocates are already attempting to make gun control a central tenet of the debate.

CNN, which is hosting the contest, posted a video on its Facebook post soliciting questions. As of Monday night, the two most popular responses came from two family members of victims of violent shootings, both of whom are advocates associated with Everytown.

“My mum, Dawn, was the Principal of Sandy Hook School. She was shot and killed along with 25 others almost 3 years ago,” Erica Lafferty Smegielski said in a comment that has garnered over 1,500 likes. “What do you think are the top three things the next President needs to do in order to make sure fewer families have to go through the pain that mine has?”

Andy Parker, whose daughter, Alison, was horrifically shot and killed on live television earlier this year, also posted a question.

“My daughter, Alison, was living her dream life as an on-air reporter in Roanoke. Then she was shot and killed on live television. There are common-sense laws that can reduce this senseless violence. As President, will you commit to working towards requiring background checks for ALL gun sales?” Andy Parker asked.

Where the candidates stand

The issue is a rare area on which the race’s firebrand liberal insurgent, Sen. Bernie Sanders (I-Vermont), seems vulnerable.

The Vermont senator has risen toward the top of the polls with an uncompromising progressive economic message. But Sanders’ record on gun-control is far more mixed.

Sanders — who was supported by the National Rifle Association in his first run for Congress — opposed legislation allowing the victims of gun violence to sue the manufacturer of the weapon. (He said on “Meet the Press” last weekend that he was willing to “take another look” on the issue.)

Sanders also opposed the “Brady bill,” which mandated federal background checks on firearm purchasers, on the grounds that it imposed a mandatory waiting period for handguns.

Sanders’ rivals appear to have taken notice.

Hayley Morris, a spokeswoman for O’Malley, emphasised his record on gun violence in a wide-ranging conversation Monday.

“Back in 2002, 2003, he was one of the first voices calling for an assault-weapons ban. And he continued to work on that until he passed some of the toughest gun safety reforms in the country,” Morris told Business Insider.

Clinton, who released her gun-violence plan less than a week after the Oregon shooting, has also been more outspoken on the need for new measures, including universal background checks.

“It is just beyond my comprehension that we are seeing these mass murders happen again and again and again. And as I have said, we have got to get the political will to do everything we can to keep people safe,” Clinton told CNN earlier this month.

Compare that to 2008. Then, Clinton criticised then-Sen. Barack Obama for his much-ballyhooed comments that rural voters “cling to their guns or religion.”

Clinton, who repeated a story about her father teaching her how to shoot as a kid, inspired Obama to quip that the former first lady was “talking like she’s Annie Oakley!”

“Previously, people talked about an intensity gap, that, ‘Yeah, everybody agrees, but this isn’t anybody’s No. 1 issue,'” said Lamb, the communications director at Everytown. “And we’ve seen that change dramatically in the last few years because of the big events, and the ones that don’t make as much news.”

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