With the nation’s latest shooting massacre came the latest calls by gun-control advocates for tougher laws. But those views, once shared by most Americans, drew little reaction on Friday from a country and its political leaders whose sentiments have shifted dramatically over the past two decades.

The Violence Policy Center and dozens of other gun-control groups issued a joint statement blaming an “out-of-control, militarized gun industry” for the shootings at a movie theater in suburban Denver early Friday that killed at least 12 people and left dozens injured.

Some of the groups directed their frustration at President Obama, who was once a vocal advocate for stricter gun laws but has done little to change them.

Following remarks the president made in Fort Myers, Fla., where he cut short a campaign swing and told the nation that he is “heartbroken” about the shootings, the Brady Campaign to Prevent Gun Violence responded by saying: “We don’t want sympathy. We want action.”

It’s not likely to receive any, in part because of the politics around the issue, which even gun-control advocates acknowledge aren’t in their favor.

“It’s pure calculus at this point, and the calculus is that it’s not worth touching this issue,” said Dan Gross, president of the Brady Campaign.

That calculus, he and others said, includes the power of the National Rifle Association and its 4 million members — many of whom live in critical swing states, such as Virginia and Ohio, that are likely to determine this year’s presidential election.

There is also the reality that no gun-control measures could pass through Congress, where Republicans control the House and where, even in the Democrat-controlled Senate, support for gun rights is strong.

National polling, too, helps explain Obama’s position on the issue. A 2010 Gallup survey shows that support for greater gun restrictions has fallen 34 percentage points over 20 years, while support for fewer restrictions or the status quo has grown by about that amount.

Two of the top priorities for gun-control advocates are a ban on assault weapons and an expansion of required criminal background checks to include buyers at gun shows. But those measures wouldn’t have stopped James Holmes, the alleged shooter in Colorado, from buying most of his firearms. A ban on assault weapons may have blocked his purchase of an AR-15 assault rifle, but he still would have been able to buy the two pistols and shotgun he allegedly brought with him to the movie theater. All four weapons were purchased legally after background checks.

There’s no point, some Obama supporters say, in taking on issues with little hope of progress.

“Nothing happened when a congresswoman was shot in the head,” said Matt Bennett, a co-founder of Third Way, a centrist think tank in Washington. “Nothing happens when dozens of kids are shot in a movie theater. It’s a terrible truth, but it is the truth nonetheless.”

He was referring to the shooting of then-Rep. Gabrielle Giffords (D-Ariz.) last year in Tucson, after which Obama wrote an op-ed piece in the Arizona Daily Star calling for a “new discussion” on how to make the nation safer and keep guns out of criminals’ hands. No concrete legislative proposals emerged.

Speaking to reporters on Air Force One en route to Fort Myers, White House press secretary Jay Carney mirrored closely what was said in the aftermath of the Giffords shooting: “The president believes that we need to take common-sense measures that protect Second Amendment rights of Americans, while ensuring that those who should not have guns under existing law do not get them.”

In the Illinois Senate and the U.S. Senate, when his constituents included crime-weary residents of inner-city Chicago, Obama was a vocal advocate for stricter gun controls. He even mentioned his support for an assault-weapons ban during his nomination acceptance speech at the Democratic National Convention in 2008.

But as president, Obama has focused primarily on improving enforcement of existing laws. The Justice Department on Friday released a background memo detailing the administration’s efforts to make required background checks more thorough. Examples include better reporting of arrest and conviction records and of people who are prohibited from buying guns for mental-health reasons.

The administration has made little mention, however, of a priority Obama promised on the campaign trail in 2008: extending background checks to sales at gun shows. The checks are not required in some states.

Like Obama, Republican challenger Mitt Romney has supported a ban on assault weapons in the past, while he was governor of Massachusetts. But since then, he has adopted a hard line against all gun controls. At a speech to the National Rifle Association this year, he suggested that Obama would try to restrict guns in a second term.

The NRA and other gun-rights groups have sought to cast Obama as dangerously anti-gun. The Web pages for the NRA and the Gun Owners of America are stocked with accusations that the president is sneaking gun restrictions into international treaties and executive orders.

One theory is that the Obama administration intentionally allowed automatic weapons to get into the hands of Mexican drug cartels to prompt more gun violence in this country and scare Americans into supporting stricter gun laws.

“He’s a very active and aggressive president when it comes to undermining Second Amendment rights,” said John Velleco, director of federal affairs for Gun Owners of America. “His administration supports a renewal of an assault-weapons ban based on the gun violence in Mexico along the border. Yet he doesn’t acknowledge any role in his administration in fueling the violence. It’s almost as if the evidence wasn’t there.”

In his speech Friday, Obama focused on the nation’s sorrow. If the past is a guide, it is a subject he will stick to in coming days.

“If there’s anything to take away from this tragedy, it’s the reminder that life is very fragile,” he said. “Our time here is limited, and it is precious. And what matters at the end of the day is not the small things, it’s not the trivial things, which so often consume us and our daily lives. Ultimately, it’s how we choose to treat one another and how we love one another.”