Story highlights Bernie Sanders said his campaign was assembling a "comprehensive package" of plans to address gun violence in the United States, but the plan has not been introduced

Gun control has been a nagging issue for Sanders since he launched his campaign last year

Hillary Clinton has successfully used the issue as a wedge to hurt Sanders' liberal bona fides

Las Vegas (CNN) In response to a series of mass shootings last year, Bernie Sanders said that his campaign was assembling a "comprehensive package" of plans to address gun violence in the United States.

Months later, the insurgent candidate has failed to live up to that pledge.

Sanders' campaign has yet to issue a detailed policy paper on gun control, something the candidate has done for a slew of other economic and core-Democratic issues. And his campaign does not list fighting gun violence on his more than 20-position-long issue page on his website.

Sanders' aides did not respond to multiple requests about why his campaign has not announced a "comprehensive" gun plan as promised.

Gun control has been a nagging issue for Sanders since he launched his campaign last year. While Sanders has appealed to the left of the party on campaign finance, education and health care, guns are one issue that Hillary Clinton has successfully used to hurt Sanders' liberal bona fides. That matters in a state like South Carolina, where the Vermont senator still needs to grow his base of support.

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