Washington (CNN) The mass shooting at a high school in Florida on Wednesday is the latest in a string of similar tragedies over the last few decades. It has some asking for Congress to tighten gun control measures , which Congress has been hesitant to do in the past . While it's unclear whether lawmakers will actually move to pass legislation this time around, it's important to keep in mind how public opinion (not just lobbying groups ) makes it difficult for gun control to pass Congress.

1. The parties are trusted about equally when it comes to guns

During debates about gun control, you'll often hear Democrats complain that 90% of Americans are in support of universal background checks. Then you'll see most Republican lawmakers vote against expanded gun control measures. And finally, you'll see few Republican lawmakers electorally punished for voting against universal background checks. Why?

Part of what's happening is that voters' views on background checks aren't really representative of their views on gun policy overall.

Consider all live interview polls taken over the course of 2017. In them, the question of whether respondents leaned more toward the Democratic or Republican Party on gun policy was asked times . On average, 1 percentage point more Americans said they leaned more toward the Republican Party than the Democratic Party on gun policy.

Until that changes, Republicans don't really have much of an electoral reason to change their minds on gun control.

2. Americans are very polarized on gun policy

Last year, I l ooked at 10 different issues ranging from abortion to free trade to same-sex marriage that the Pew Research Center polled on. Americans were more polarized on gun policy than any other issue except building a border wall with Mexico. In Pew's latest poll on the subject, 79% of Republicans favored protecting gun ownership rights over limiting gun access. That compares with 20% of Democrats who felt the same way.

In other words, there was a stunning 59 percentage point partisan gap on the issue.

Indeed, as Nate Cohn of The New York Times pointed out , few issues were more predictive of vote choice in the 2016 election than gun ownership. Donald Trump won voters in households with guns in every state but Vermont. He lost voters in households without guns in every state but West Virginia. (There wasn't enough data in Wyoming to know what happened there.)

No doubt the lack of action from Republican lawmakers on gun control is at least partially attributable to them listening to their base.

3. Public opinion momentum is against gun policy

When Pew first asked Americans whether they were more in favor of protecting gun rights or controlling gun ownership in 1993, 35% said gun rights and 57% said gun control. By March 2000 (a year after the shooting at Columbine ), 29% said gun rights and 67% said gun control. In the latest survey from Pew, 47% said protecting gun rights was more important than gun control, compared to 51% who said gun control was more important than protecting gun rights.

The rise in those who think protecting gun rights is more important than gun control has been driven mostly by Republicans . Back in March 2000, 40% of Republicans and 19% of Democrats thought that. Since that time, Republican support for gun rights has grown by 39 percentage points. It's grown by just 1 point among Democrats.

4. Gun advocates are more passionate

Last year, Gallup asked Americans whether they would vote only for a candidate who shared their views on gun policy or whether it was one of many important factors they would consider before voting. Among gun owners, 30% said they could vote only for someone who shared their viewpoint. Among those who didn't own guns, it was 20%. Not only that, but since 2000 the percentage of gun owners who said gun issues were key to their vote climbed by 17 points. It rose by just 10 points among those who didn't own guns.

Pew has made similar findings to Gallup. Gun owners are 9 points (21% to 12%) more likely to have contacted public officials about gun policy than those who don't own guns. Americans who favor loosening gun laws have been 7 points (22% to 15%) more likely to contact public officials than those who favor stricter gun laws.

Even if some Republicans were tempted to support stricter gun control, these numbers suggest that they might be pressured into voting against it because gun rights advocates are more likely to make their voices heard.

5. Support for gun control may momentarily rise

Support for gun control measures sometimes rises after mass shootings . After the Columbine shooting and the shooting at Sandy Hook , Americans were more likely to support gun control than in the time periods surrounding them. That has at least to do with the fact that the media covered these shootings to a much greater extent than they have other recent shootings. If this shooting in Florida receives a lot of media attention (compared with other shootings), it's conceivable that support for gun control may temporarily rise.

Again, though, past history suggests that any bump in public opinion in favor of gun control will not hold. The long-term trend is against gun control.