The 1960s were known for their turmoil, but the degree to which guns were a factor is sometimes overlooked. Not only was a president assassinated, but an ex-Marine opened fire from an observation deck in Austin, Texas, and the homicide rate leaped by more than 50 percent, driven by fatal shootings. Gun sales soared, prompted by fears of violence and rioting.

But the mayhem and violence didn’t seem to move a Congress that refused to take gun-control legislation seriously. It would not even approve a proposal to outlaw the mail-order purchase of rifles, like the one Lee Harvey Oswald bought for $19.95, plus shipping and handling, and used to kill President John F. Kennedy.

One of the few major gun control measures enacted, in California, was a reaction not to violence but to the Black Panthers’ exercising their right to bear arms by patrolling with loaded rifles.

The political calculus began to change on April 4, 1968. The Rev. Martin Luther King Jr. was gunned down in Memphis, Tennessee. Nine weeks later, Sen. Robert F. Kennedy was fatally shot in Los Angeles.

Finally, gun control became a possibility — at least in the hands of President Lyndon B. Johnson, a master at turning tragedy into legislative gain. He had used the death of President Kennedy to pass the Civil Rights Act, and wrung the Voting Rights Act from the Bloody Sunday march in Alabama from Selma to Montgomery. Now he would try for the Gun Control Act.

Today, it’s not clear that any shooting could be awful enough to embolden Congress to thwart the National Rifle Association. But even back then, the NRA throttled much of what Johnson intended to do.

“The voices that blocked these safeguards were not the voices of an aroused nation,” an angry president said at the bill signing. “They were the voices of a powerful lobby, a gun lobby, that has prevailed for the moment in an election year.”

He called on “those of us who are really concerned about crime” to fight for stronger laws. “We have been through a great deal of anguish these last few months and these last few years — too much anguish to forget so quickly.”

The new law outlawed gun sales to felons, drug abusers, minors and those with mental illness; banned most out-of-state and mail-order gun sales; and sharply curbed imported weapons, including the cheap, tiny pistols used in many homicides. It remains a cornerstone of federal gun law today.

The King assassination spurred the legislation not just because it horrified the nation, but also because it prompted unrest across the country, including in Washington, where lawmakers watched rioters come within blocks of the White House as thousands of federal troops were mobilized.

“It was in Congress’ backyard, so they didn’t have to read about it in the newspapers. They could see it,” said Larry Temple, a high-ranking aide and special counsel to Johnson. “The death of Dr. King and the resulting riots in Washington had an impact on Congress and what they wound up doing.”

But it wasn’t until June 5, when Sen. Kennedy was assassinated, that the logjam looked like it would break. A day later, a modest gun-control proposal that had languished passed Congress, raising the age to buy handguns to 21.

Still, Johnson wanted something far more sweeping. He proposed to treat guns like cars: They would be registered and their owners would be licensed. Had something like this passed, gun-control proponents say, the United States today might look more like Britain or Australia, countries where guns are tracked and gun violence is a fraction of what it is here.

“He said, ‘We have about 10 days or two weeks to get it passed,’” recalled Joseph Califano, his chief domestic adviser. “‘If we don’t get it out of committee by then, the NRA will kill us.’”

This time, there has been no similar urgency in Washington, even as hundreds of thousands of protesters in the capital and elsewhere have demanded changes after the killing of 17 students and staff at a high school in Parkland, Florida.

Crime is less a concern, as the murder rate has fallen sharply since the ’60s. But mass shootings have become frighteningly common. Anyone — or anyone’s child — could be a victim, at a school, a concert, a church, a movie theater or a nightclub.

And while a smaller percent of households own guns, the country has more of them, and they are deadlier: Semi-automatic rifles like the AR-15 have become the weapon of choice in the largest recent mass killings, leading to death tolls in the dozens.

Most people today favor tighter gun restrictions, polls indicate, just as they did a half-century ago. But the NRA also wields political power disproportionate to the size of its membership, as it did then. In 1968, the organization was not yet as uncompromising as it is today. But it used tactics that would feel familiar now.

It flooded its members with sky-is-falling warnings about the government taking away gun rights, and urged them to hound lawmakers. In a letter to 900,000 NRA members in June 1968, the organization’s president, Harold W. Glassen, said that the “right of sportsmen” to lawfully own and use firearms was “in the greatest jeopardy in the history of our country.”

Frustrated gun-control backers called it “calculated hysteria and distortion.” But it was profoundly effective. In its coverage that month, The New York Times called the gun lobby among the most effective in Washington, citing the association’s ability to get “sportsmen, farmers and gun lovers to put pressure on their congressmen.”

Soon, Johnson’s favored provisions were shorn from the bill by his old cadre of fellow Southern Democrats.

“Strom Thurmond is hostile as hell, and so is Jim,” — James O. Eastland, D-Miss. — “and they’re mutilating the bill as it is,” the leader of the Senate Republicans, Everett Dirksen of Illinois, told Johnson in a recorded phone call on July 24, 1968, that is in the Johnson’s presidential library. (Thurmond was by then a Republican.)

The licensing and registration provisions passed neither chamber of Congress, and triumphant pro-gun forces announced it was now legislation they could “live with.” To which Rep. Charles S. Joelson, D-N.J., responded: “I suggest that tens of thousands of Americans can die with it.”

The Gun Control Act was signed into law that fall.

Two years later, the NRA helped defeat the re-election bid of a leading Senate proponent of tough gun laws, Joseph D. Tydings, D-Md., a man who had won his seat just six years earlier in a landslide.

By now the NRA has perfected the art of going after lawmakers who defy the organization. That is one reason the demands of mass shooting survivors and their allies, now led most visibly by the Parkland students, remain so far apart from the measures Congress is considering.

In 1956, after his house was bombed, King applied to the local sheriff for a permit to carry a concealed handgun. He was denied on the grounds that he was “unsuitable,” according to Adam Winkler, the author of “Gunfight: The Battle Over the Right to Bear Arms in America.”

Friends and relatives who feared for his safety urged him to hire a bodyguard and armed watchmen, he wrote in his autobiography. But soon, he and Coretta Scott King, his wife, reconsidered and gave up the one gun they owned. “How could I serve as one of the leaders of a nonviolent movement and at the same time use weapons of violence for my personal protection?” he wrote.

Fifty years ago, the death of great leaders prodded Congress to act on gun control. Now, at a similar juncture, it is the death of schoolchildren that has stirred the makings of a movement. It remains uncertain whether the current movement for gun restrictions will result in meaningful reform. So far, the main impetus is in state legislatures.

“Even in Republican-controlled states it appears there is at least some openness to doing something, building on the foundation laid over the last five years in less conservative states,” said Adam Skaggs, chief counsel of the Giffords Law Center to Prevent Gun Violence. But he said Congress may not do much unless midterm elections shake things up.

For King, who would have turned 89 in January, getting rid of his gun helped him reckon with his mortality and focus on his movement.

“From that point on, I no longer needed a gun nor have I been afraid,” he wrote. “Had we become distracted by the question of my safety we would have lost the moral offensive and sunk to the level of our oppressors.”

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