Polls routinely show that a majority of Americans support gun-control legislation, such as background checks, gun licensing, assault-weapons bans and red-flag laws. So why hasn’t public opinion filtered up to Washington, which hasn’t passed a major gun-control law in more than 20 years?

On Thursday, Quinnipiac University released a poll that shows that voters strongly support stricter gun laws, and support for some of these proposals is overwhelming. Jim Sciutto of CNN shared the breakdown and asked the question that spurred this post.

It’s an interesting question. Let’s try to answer it.

There’s no one reason public support for stricter gun laws hasn’t translated to stricter gun laws, but here are some major factors:

For decades, opponents of this kind of legislation have been better organized. The National Rifle Association has been one of the most successful lobbying and advocacy groups of the past 40 years. NRA officials routinely talk about their army of grass-roots supporters.

A Republican strategist who used to work in the Senate told me that when guns were being debated, the phones wouldn’t stop ringing with people who oppose stricter gun laws.

Gun-control opponents are catching up — they outspent the NRA last year for the first time — and the NRA is weakened internally. But this balance of power takes time to shift and to make an impact on lawmakers.

People who support gun-control laws also aren’t sure how it affects them. Jim Kessler has studied this issue with the center-left think tank Third Way, and they found that people outside of urban areas who aren’t affected daily by gun violence “would be perfectly fine if [a background check law] passed, but it was more a shrug of the shoulders than a shout to the rafters.”

“There’s a difference between support and popularity,” Kessler said.

Of course, that dynamic could be changing now that Americans feel as if mass shootings can happen anywhere, anytime. A recent Fox News poll asked what people think is the bigger threat, a mass shooting by a fellow citizen or an international terrorist threat. Even Trump voters said a mass shooting.

The details are where this gets bogged down. And that’s true both in lawmaking and public opinion. When you ask people: “Do you support background checks for all gun sales?” pollsters regularly get support in the 80-to-90-percent range. But if you ask people: “Do you support background checks for all gun sales, including one you sell to your cousin down the street?” that number probably wouldn’t be as high.

Polls have also used different wording in asking about assault weapon bans and found varying levels of support. A fall 2018 survey by the Public Religion Research Institute found 65 percent support for “a ban on semiautomatic assault rifles.” A Gallup poll conducted around the same time elaborated on what a “ban” might mean (you can’t possess an assault rifle) and found a relatively low 40 percent in favor of it.

But Katie Peters, with the gun-control group Giffords, founded by former congresswoman and mass shooting victim Gabrielle Giffords, notes that this hasn’t stopped the House of Representatives from passing background-check bills this year.

The right is particularly hardened on this issue. A July NPR-PBS NewsHour-Marist poll found that 57 percent of the public supported a ban on assault-style weapons. But fewer than 3 in 10 Republicans supported it. That’s pretty typical of the gun debate.

But Peters points out there are cracks in the right. Some Republicans are openly considering gun-control legislation. Even Senate Majority Leader Mitch McConnell (R-Ky.), who is up for reelection next year in a pro-Trump, pro-gun state, has said that background checks and red-flag laws will be “front and center” when Congress returns in September.

These numbers might be moving the political dial, but it takes time. That time is moving quickly, Peters said. Just look at how the 2020 Democratic presidential candidates are embracing stricter gun laws and how House Democrats have prioritized this issue after winning the majority in 2018. These politicians think it’s a winning issue to champion.

“These candidates know demonstrating support to strengthen gun laws is not just the right thing to do, it’s politically smart. (They’re looking at those poll numbers, too!)" Peters said.

Scott Clement contributed to this article.