The NRA announced earlier this month that it would support measures to limit the sales of a device called a bump fire stock, which makes non-automatic weapons fire as if they’re automatic and which was used in the mass shooting in Las Vegas. Some congressional Republicans have also signaled that they’re open to legislation that would outlaw the device. Was the massacre in Las Vegas, the deadliest mass shooting in recent U.S. history, enough to push a GOP-controlled Congress and White House to pass some form of gun-control legislation?

The idea that events should change policy is appealing. After each incident of gun violence in the U.S., someone retells Australia’s story. Twelve days after a mass shooting there in 1996, the legislature took up anti-gun measures, including a buyback program and various restrictions on the types of guns that could be sold. But in the U.S., gun control policy has often appeared impossible to pass at the federal level: A common response after Las Vegas seemed to be, “If nothing changed after Sandy Hook, nothing will change now.” Does public opinion — and, as a result, the policy process — actually respond to events? Let’s look at a few schools of thought in political science and public policy.

1. Sure, events matter

According to one major theory of policy change, a “focusing event” can help push policy in a new direction. These kinds of events, which include natural disasters, terrorist attacks and other crises, can turn the public’s attention to a problem and also demonstrate to policy-makers that existing systems aren’t doing enough.

Major events that dominate the news — such as the Sept. 11, 2001, terrorist attacks and the 1989 Exxon Valdez oil spill — have the potential to alter how the public thinks about an issue (what scholars call “frames”). Because of their ability to shift public opinion, these moments can help interest groups mobilize and pressure elected officials for change. After the Exxon Valdez spill, for example, Congress passed the Oil Pollution Act of 1990. After the Sept. 11 attacks, we saw the passage of the USA PATRIOT Act, which strengthened the power of the federal government to investigate perceived terrorist activity, and the creation of the Department of Homeland Security.

2. Well, they might matter

It seems intuitive that a major crisis would reshape the politics of an issue. But not so fast.

Although events may dominate the news, that’s not the same thing as changing how citizens and policy-makers think and talk about them. As Thomas Birkland wrote in a study of the event’s impact, “September 11 only threw open the window of opportunity for policy change based, in large part, on preexisting ideas.” For example, the Department of Homeland Security was not a brand new idea when it was formed after Sept. 11; lawmakers had been debating for several years about how to coordinate counterterrorism efforts. In other words, the attacks brought terrorism to the top of the priority list, but they didn’t introduce new ways of thinking about how to prevent terrorism.

A similar thing happened after Hurricane Katrina. The storm prompted new discussions and some policy change, especially in relation to how the Federal Emergency Management Agency operates. But a major study of Katrina media coverage found that instead of challenging or reframing existing ideas about disasters and their victims, Katrina coverage fell into old patterns, such as employing racial stereotypes about looting and using the “war zone” metaphor to describe the scene. Frames like these make it unlikely that news stories will elicit much public sympathy for victims or put disaster relief issues atop the agenda.

The other way a major event can fail to change public opinions and policies is when its cause is contested. Our understanding of why an event happened is shaped by politics and social factors, argues public policy scholar Deborah Stone. She found that “complex cause is sometimes used as a strategy to avoid blame and the burdens of reform.”

This idea describes the debate after mass shootings pretty well; gun-control advocates push stories about the role weapons played in the deaths while gun-rights advocates point to other factors, like mental health problems or declining public morals, as the root cause of the problem. Perhaps as a result of the many competing explanations for why these incidents occur, public attitudes about guns and gun control changed very little after the Sandy Hook shooting.

The principles we invoke when we talk about these events can matter too. The current gun conversation typically presents the issue as a clash between liberty and public safety. “Constitutional imagery and symbolism frame political discourse,” Robert Spitzer writes in his book “The Politics of Gun Control.” There’s evidence that people respond differently depending on whether they think about guns as a public safety issue or an individual rights issue. It’s likely that the public will need to agree on a framework for the issue before we see any widespread shifts in public attitudes.

3. No, events don’t change public opinion

There’s a lot of evidence that attitudes (and policies) change not as the result of a big crisis event in the news but because perceptions have evolved more gradually. The legalization of recreational marijuana is a good example of this phenomenon. Support for legalizing the drug had been growing for years before the recent spate of state laws decriminalizing its use were passed. These changes have been attributed by experts to ideas about the war on drugs as a civil rights issue, perceptions that enforcement of drug laws is not effective, and broad social changes. Marijuana policy expert John Hudak noted in his book, “the hippies got older and had their own families.” State policy changes, including the legalization of medical marijuana, also seem to have contributed to the shift. But there’s been no major catalyzing event that might move public opinion.

Similarly, there has been a fairly rapid attitude shift in support of same-sex marriage over the past 15 years. There are many factors that may be driving this change — as with marijuana, there are big generational differences and the culture has shifted considerably. Activist efforts are also at the root of this shift. This has yielded some lessons about how attitudes change, including more evidence that language matters. In efforts to increase support for same-sex marriage, frames that highlighted equality proved to be an important element in bring together a coalition that crossed ideological, racial and religious lines. In a recent study of attitude changes on this issue, researchers found that people were much more likely to be swayed by messages from people with whom they shared an identity — even if it was as trivial as sports fandom.

In both cases, attitude and policy change has come not from a major event that changes people’s understanding of a topic, but rather from more long-term structural changes in society as a whole that result in a gradual reframing of the issues at hand.

So where does this leave us on guns?

It’s complicated. Too complicated to make a blanket statement about how major events or crises affect public opinion or policy. The historical record suggests that major events can lead to policy change by prioritizing an issue, but they don’t necessarily change opinions about that issue.

That’s particularly true if the issue has been prominent in the national debate for some time and is deeply polarized, the way gun control is. As my colleague Harry Enten noted, public opinion on gun control is highly partisan and somewhat tough to pin down. That fact, combined with the increasing polarization of politics in the U.S. more generally — there’s plenty of evidence that Republicans and Democrats view the same events very differently these days — means that public opinions are pretty well set.

That doesn’t mean policy change is impossible, though.

For one, while gun control as a big-picture issue remains divisive, there is some bipartisan agreement on specific policies. Many Republicans support some forms of gun control. Background checks, for example, are popular across different partisan groups.

Second, the relationship between public opinion and policy change isn’t so clear cut. Political scientist Matt Grossmann has argued that policy change occurs not when public pressures mount but when elites can agree on specific policy proposals, which is often sorted out behind the scenes. This framework is likely to apply to the gun question. In a system like ours where policy change is difficult, a well-organized, well-funded group of citizens who care a lot about an issue can have an advantage over a much larger majority of people who disagree but feel less strongly. The NRA is a powerful organization. OpenSecrets.org reports that gun rights groups spent $10.6 million on lobbying in 2016, compared with the $1.7 million spent by gun control and safety groups. In other words, we can’t expect that public opinion will produce policy change on its own — major shifts also require organization.

Furthermore, just because voters have deep partisan ties, that doesn’t necessarily mean they are set in their ways. Strong partisanship also means that party leaders have an impact on what citizens think. Some social science research shows that conservatives are more likely to support a liberal position if they think President Trump supports it — see, for example, recent swings in opinion on free trade and Russia. That same principle also applies to liberals. Given the slight movement among Republican lawmakers this month around the topic of bump stocks, it’s possible that elites won’t act because of widespread public pressure, but rather that public opinion will change because elites act.

The kinds of events that are associated with policy change are dramatic and lend themselves to a clear narrative — sympathetic portrayals of victims and a spelled-out connection between the problem and the policy proposals intended to address it. These kinds of events help policy-makers get together on the details. They also make opposition politically difficult. In terms of gun violence, we’ve now had several of these events in recent memory. If the Las Vegas shooting is the one that changes things, it may not be because of the event itself, but because of longer term political pressures that have been building for years.