Phil Murphy, the Democratic nominee for governor, pledged Thursday to enact many of the gun-control measures that Republican Gov. Chris Christie has denied if he is elected in November, raising the likelihood that so-called smart guns will hit the market in New Jersey and .50-caliber rifles will be purged from it.

But Murphy wouldn't stop there.

In a conference call to accept the endorsement of a super PAC led by former Democratic Rep. Gabrielle Giffords, Murphy said he is considering a new tax on gun sales to support law enforcement and mental health programs, as well as a host of other gun-control measures he characterized as "common sense" measures that balance Second Amendment rights with public safety.

The tax proposal and other gun-control measures have been long-standing ideas for Murphy, but he renewed his pledge during Thursday's call to follow through on a gun safety agenda to counter the actions of Christie over the last several years.

New Jersey already has some of the strictest gun regulations in the country, so rigid that Christie has regularly issued pardons to otherwise law-abiding gun owners who he has said have become victims of the law. And virtually any proposal to tighten those laws would likely anger gun-rights groups and conservatives who, like Christie, view New Jersey as far too restrictive for gun owners.

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But Murphy said Thursday that he is "not alone in wanting strong gun safety laws in our state." And as he has on so many fronts, from spending to governing style, Murphy promised to reverse Christie's course.

"You can assume the measures he’s vetoed we would have signed, and we’ll endeavor to do so," Murphy said on the conference call, where he accepted the endorsement of Americans for Responsible Solutions. The super PAC was started in 2013 by Gabrielle Giffords, a former congresswoman from Arizona who was shot during a public event in 2011, and her husband, West Orange native Mark Kelly, who joined Murphy on Thursday's call.

Christie once campaigned for stronger gun laws, but he has tacked right in recent years.

After the 2012 gun massacre at an elementary school in Connecticut, Christie proposed banning .50-caliber rifles, then vetoed the bill because, he said, it went too far.

He also vetoed a proposal to require retailers to sell smart guns — personalized firearms that use technology to prevent children or unauthorized users from firing the weapons.

Other measures he's rejected include ones to limit ammunition magazine sizes and to prohibit certain convicted criminals from possessing firearms (that one duplicated a federal ban, Christie said).

Murphy said he would also favor laws requiring gun safety training for owners, keeping firearms out of the hands of people with mental illnesses, strengthening regulations on gun transfers and working with neighboring states on gun violence prevention efforts.

Taxing guns

Murphy's plan to add a tax on gun sales is among the latest increases he has proposed, and it is all but certain to provide his critics with more ammo to portray him as a tax-and-spend liberal who will dig the state into a fiscal hole.

Murphy, who is leading comfortably in the polls against Republican Lt. Gov. Kim Guadagno, is banking on $1.3 billion in new revenues, should he win, from new taxes on high earners, marijuana and large corporations, his campaign told Observer. Earlier this week, Christie warned that the $1.3 billion in new revenues would be only the beginning.

"I'm telling the people of New Jersey right now: He's coming for your money," Christie said, labeling Murphy, who was raised outside Boston, "a Massachusetts liberal — the worst kind."

Murphy did not have many details of the gun tax Thursday.

"We have not picked a particular level yet. That’s something we’re still trying to work through," Murphy said.

The campaign has discussed taking tax money on gun sales and "sending it directly back" to law enforcement, as well as mental health programs and other community-based organizations.

The idea, he said, is that there are many reasons besides gun safety laws "that lead people to do bad things with guns." He said "there's no reason why we can't address both" law enforcement and mental illness programs to try reducing the level of gun violence.

Ricky Diaz, a spokesman for Guadagno, did not comment on the gun sales tax, but said that as a former county sheriff and federal prosecutor, Guadagno "supports efforts to enforce our state’s gun laws already on the books instead of passing new laws that restrict the rights of law-abiding gun owners."

Kelly, Giffords' husband and the co-founder of the super PAC, said the organization supports other efforts aimed at limiting gun violence, such as closing private gun sale loopholes, enacting "extreme risk" protection orders and improving firearm safety technology.

He said many of the country's leaders are "in the grips of the gun lobby," and his organization's goal is to counter that influence and help to elect people who can "bring some balance back" to the discussion about gun laws and public safety.

Kelly did not say how much money his organization plans to spend on the November election in support of Murphy. As a super PAC, the organization is barred from coordinating with the Murphy campaign.

"We’re mapping out our strategy," Kelly said. "Just know that we are incredibly committed to this race and to the state of New Jersey."