After the slaughter last month of 20 schoolchildren at Sandy Hook Elementary in Newtown, Conn., cynics said the response wouldn’t be any different from those to the many mass killings that came before. After the tiny caskets disappeared, so would the shock, the grief and the resolve. Emotion, after all, is no match for the National Rifle Association.

What the cynics didn’t take into account is that Sandy Hook changed the one person who matters more than almost any other: the president. And he can count on the support of the one group that has more authority than almost any other: the parents of the children who died.

If Bill Clinton found his voice after the Oklahoma City bombing, Barack Obama found his after the Newtown shootings. The day he delivered his remarks at a memorial service there, Obama had sat in an empty theater, working on his speech and watching the dress rehearsal of his daughter Sasha’s Christmas pageant, which he would miss.

He was a father, not a president. He took Newtown to heart. After mentioning guns only rarely in four years, he announced on Jan. 16 the biggest battle against gun violence in decades. That which he could do on his own by executive order, he would. The rest of the fight he would take to Congress.

Of course, taking on the gun lobby isn’t exactly courageous. The public is on the side of more regulation: According to a recent Washington Post-ABC News poll, 88 percent of respondents favor background checks on people buying guns at gun shows, 76 percent support checks on buyers of ammunition, and 71 percent back a new federal database that would track all gun sales. Some 65 percent also support banning high-capacity magazines.

When will it dawn on the majority of the nonviolent millions that just because our politicians do, we ourselves don’t have to stand helpless at the savage slaying of schoolchildren? Life doesn’t go on for them. It shouldn’t be the same for us.

We’ve conceded so much to the NRA largely because cowardly members of Congress have. If you’re a lobbying group and can plausibly threaten a single member of Congress with defeat, hordes of others will cower in fear — and that includes Democrats. The most intense emotion in Congress right now isn’t remorse over the lost children but fear of losing your seat.

Maybe the president could garner some support among members of Congress by showing them that support of reasonable regulation may help them stay in office. He has a vaunted political organization that is at least the equal of the NRA. Promise to mobilize it to save those who vote for his proposal. Split the NRA leadership from its members, the way workers were separated from union bosses. Make the NRA even more Republican and rural, and increasingly marginalized. Defeating a congressman because he supported gun regulation should be like defeating someone because he supported seatbelts or a smoking ban on airplanes.

The Founders had gun laws so intrusive that, were they running for office today, the NRA wouldn’t endorse them. Gun ownership was denied to slaves, free blacks, and any white man who refused to swear loyalty to the Revolution. Those given ownership had to report for frequent musters of the citizen militias, at which their guns were inspected.

And these were muskets, not Bushmaster rifles. Even Supreme Court Justice Antonin Scalia, in affirming the individual right to bear arms under the Second Amendment, noted that there is considerable room to regulate that right.

Before the president announced his actions, the NRA released an ad that targeted his daughters, whose school has armed guards — the implication being that the president doesn’t want your children to be as safe as his. This is one of those moments to wish that the cool Obama could be more like hot- tempered New Jersey Gov. Chris Christie. When a voter once asked Christie where his children went to school, he shot back: “None of your business.”

Fortunately, there are many more parents (about 149 million) than NRA members (about 4.3 million). Obama should pack the gallery at next month’s State of the Union with parents who have lost children to gun violence. He should keep their sons and daughters vivid in our memories, as he did at this week’s announcement, with stories about their passions for painting and bike-riding. He should campaign for gun control the way he did for healthcare reform.

The bereaved parents of Sandy Hook have joined together as a group called Sandy Hook Promise. At its founding, David Wheeler asked, “What is it worth doing to keep a child safe?” On Dec. 14, the Wheelers lost their 6-year-old son Benjamin. In the immediate aftermath, Wheeler and his wife comforted their surviving son, Nate, with the assurance they would do anything to protect him — and then realized they should make the same promise to Ben.

Like other children that day at Sandy Hook, Ben probably thought that Mom or Dad would be there any moment to rescue him. The least the rest of us can do is be there now.