Rifles for sale at a gun shop in Merrimack, N.H. (Dominick Reuter/AFP/Getty Images)

Mark R. Warner, a Democrat, is a U.S. senator from Virginia.

I keep coming back to April 17, 2013.

That was the day I voted for legislation that would finally require a criminal-background check for all firearm purchases.

It was also the day I voted against legislation banning military-style assault weapons. While I was far from the deciding vote, I have nevertheless wrestled with that “no” vote ever since.

At the time, the Senate was voting on several gun-violence-prevention proposals, trying to find a bill that could get 60 votes. To me, it was clear that strengthening the background-check system would be the single most effective way to begin to stem the tide of gun violence in the United States.

However, every proposal the Senate voted on that day fell short. Congress, in what has become a sad pattern of dysfunction, failed to act.

In the years since the Senate last had a meaningful debate about gun-violence legislation, we’ve seen assault rifles and high-capacity magazines repeatedly used in mass shootings, with ever-higher body counts: Forty-nine murdered at the Pulse nightclub in Orlando. Fifty-eight killed and 422 wounded by gunfire in Las Vegas, one year ago Monday.

We’ve seen the gun lobby close its eyes to the fact that assault rifles were the weapon of choice for the mass shooters at Parkland, Fla., and at Sandy Hook Elementary School — and to the reality that these weapons can kill with an efficiency that shotguns and handguns, like the ones I own, simply cannot match.

Though I remain convinced that strengthening our background-check system is critical, I also believe we must do more to end mass shootings. So today I am signing on as a sponsor of the assault weapons ban.

I do this as a gun owner and a proud supporter of the Second Amendment. Before coming to the Senate, I served as governor of Virginia, a state with a long tradition of gun ownership. During my time in office, I signed into law a number of reasonable bipartisan bills solidifying the rights of law-abiding gun owners to purchase and carry firearms for sport and self-defense.

At the time, the National Rifle Association described me as a “valuable ally for gun owners and sportsmen.” While the NRA may have moved toward the extreme in the years since, I still believe in the Second Amendment. But like other parts of our Constitution, the Second Amendment isn’t absolute. For example, the law has long held that certain guns such as fully automatic rifles and accessories such as suppressors fall into a class of weapons requiring stricter oversight and regulation than your everyday hunting rifle.

Unfortunately, these shades of gray needed for good policymaking have given way to the black and white of polarized political warfare that’s increasingly fueled by special-interest money.

Still, I’m hopeful we can break this stalemate, disarming would-be mass shooters while still respecting the rights of law-abiding gun owners.

Restricting the sale of assault weapons is one such starting point. No doubt, there will need to be revisions and compromises before this bill becomes law.

But let’s also recognize that the features and tactical accessories that define assault weapons under this legislation were designed for a specific purpose — to give soldiers an advantage over the enemy, not to mow down students in school hallways.

We should acknowledge that while some will object to reasonable magazine-size limits, they would also force an active shooter to reload more often, buying law enforcement and potential shooting victims valuable seconds that could prove lifesaving.

And let’s agree that modifications such as binary triggers and bump stocks, which skirt the law to effectively turn semiautomatic rifles into fully automatic weapons, should never have been on the streets in the first place.

These are the core ideas behind the assault weapons ban. Some may worry that the technical challenges of defining an assault weapon may result in a law that’s either toothless or overly restrictive of gun rights. Frankly, I share those concerns, but it’s time to stop talking about the problem and do something about it.

We have cultural divisions that must be bridged, but we should not allow these differences to become excuses for inaction. No American wants criminals, terrorists or dangerously ill teenagers to get their hands on a weapon capable of so much destruction.

There is room for common ground here, and I believe it is this: Americans of all backgrounds can and should refuse to accept periodic mass shootings as the new normal, and we should demand that our nation’s leaders finally take action.

I plan to be part of the solution.