Former Maryland Governor Martin O'Malley announces his intention to seek the Democratic presidential nomination during a speech in Federal Hill Park in Baltimore, Maryland, United States, May 30, 2015. REUTERS/Jim Bourg Former Maryland Gov. Martin O'Malley (D) seems set to make gun control a cornerstone of his 2016 presidential campaign. He kicked off what his aides describe as a "major push" on the issue last week with an email to supporters where he declared he was "pissed" by the mass shooting in South Carolina.

Gun control has long been something of a political lightning rod and President Barack Obama suffered one of the biggest defeats of his administration when he made a major push for a package of gun control legislation following the Sandy Hook elementary School shooting in late 2012. While some politicians have been reluctant to confront guns, O'Malley campaign spokeswoman Haley Morris told Business Insider he has been "fearless" on the issue and plans to make it a prominent part of his 2016 platform.

"Governor O'Malley was fearless in taking on gun control in Maryland--standing up even to members of his own party to get results. This is an issue you will be hearing more about from him," Morris said.

In his email to his supporters last Friday, O'Malley declared he was "pissed" about the political climate following the June 17 shooting at a historically black church in Charleston, South Carolina that left nine people dead. Specifically, O'Malley said he was frustrated some people would wait for "the appropriate moment to say what we're all thinking" rather than "jumping to act."

"This is not the America we want to be living in," O'Malley wrote. "I'm pissed that we’re actually asking ourselves the horrific question of, what will it take? How many senseless acts of violence in our streets or tragedies in our communities will it take to get our nation to stop caving to special interests like the NRA when people are dying?"

O'Malley went on to suggest the repeated mass shootings in America are a "national crisis." Morris said the email is the start of what will be a "major push" from O'Malley during his presidential campaign. In it, he pointed to his record on gun control in Maryland, which included passing legislation in 2013 that banned assault weapons, lowered magazine capacity, strengthened state regulations for gun dealers, and required fingerprinting for gun purchases.

"I proudly hold an F rating from the NRA, and when I worked to pass gun control in Maryland, the NRA threatened me with legal action, but I never backed down," O'Malley wrote.

In his email, O'Malley outlined some of the gun control reforms he would push for if he is elected in 2016 including stronger background checks, a nationwide assault weapons ban, and steps to prevent people from buying guns on others' behalf. O'Malley described making gun control a major part of his campaign as "doubling down" on what he did in Maryland.

"What we did in Maryland should be the first step of what we do as a nation," O'Malley wrote.

O'Malley's presidential campaign has been characterized by staking out clear-cut liberal positions on major issues as he takes on Democratic frontrunner Hillary Clinton. Pushing for gun control actually puts him to the left of another liberal primary rival to Clinton, Sen. Bernie Sanders (I-Vermont), who has a voting record in line with his home state's light gun control laws.