The Centers for Disease Control and Prevention stands as one of the federal government’s premier agencies for studying public health and the behaviors that affect it, such as the links between distracted driving (texting) and fatal motor vehicle accidents. So it stands to reason that the CDC would also research the public health issues surrounding gun violence.

But it doesn’t, under a de facto 20-year ban that the National Rifle Association (NRA) got Congress to impose on taxpayer funding for such research. Yes, the organization that represents gun manufacturers and gun owners continues to convince lawmakers that the CDC should not study the effects of guns on public health. That’s despite the fact that gun-related deaths — homicides, suicides and accidental shootings — exceed 30,000 a year, on par with those killed in motor vehicle accidents.

That intrusion into the CDC’s work represents yet another example of the pervasive, and pernicious, reach of the NRA and its supporters. The lobby routinely bottlenecks reasonable gun-control measures in Congress and state legislatures. It delayed the Senate confirmation last year of Vivek Murthy as surgeon general over his belief that gun violence is a public health issue; he eventually promised not to use his office to press that point, a grotesque muzzling of a heath care professional. And the NRA’s knee-jerk response to the nation’s sickening pace of mass shootings is to urge that more people carry more guns, as though we all live in a Charles Bronson movie.

There already are more than 300 million guns in the U.S., though a minority of Americans owns them — about 1 in 4, down from a high of 30 percent in 1985, according to a report this year out of the University of Chicago. Most of that decrease can be attributed to the decline in the number of people who hunt. Despite the lower number of gun owners, however, they and their lobbyists, led by the NRA, wield a disproportionate amount of political weight.

Why ? Because they spend tens of millions of dollars on political campaigns, much more than gun-control advocates. And this is, at heart, a political issue. As President Obama noted in the wake of the Umpqua Community College mass killing in Oregon last week, this is not the only country with people suffering from mental illness, but it is the only advanced country that endures so many mass shootings. The issue isn’t mental illness; it’s too-easy access to firearms.

That needs to change. American voters who understand the need for better gun control must start countering the gun lobby by demanding that elected members of Congress make the health and well-being of their constituents their top priority. And they can begin by lifting the block on CDC research into the issue.