WASHINGTON — Time was — not that long ago — that after a mass shooting, gun rights advocates would nod to the possibility of compromise before waiting for memories to fade and opposing any new legislation to regulate firearms.

This time, they skipped the preliminaries and jumped directly to opposition.

“The most effective tool for keeping kids safe is armed law enforcement on the campus,” Texas Republican Sen. Ted Cruz said to MSNBC a few hours after a shooter killed at least 21 people in Uvalde, Texas. “Inevitably, when there’s a murder of this kind, you see politicians try to politicize it. You see Democrats and a lot of folks in the media whose immediate solution is to try to restrict the constitutional rights of law-abiding citizens. That doesn’t work.”

The speed of that negative reaction provides the latest example of how, on one issue after another, the gap between blue America and red America has widened so much that even the idea of national agreement appears far-fetched. Many political figures no longer bother pretending to look for it.

And yet, significant agreement does exist.

Poll after poll has shown for years that large majorities of the public agree on at least some limited steps to further regulate firearms.

A survey last year by the Pew Research Center, for example, showed that, by 87% to 12%, Americans supported “preventing people with mental illnesses from purchasing guns.” By 81% to 18% they backed “making private gun sales and sales at gun shows subject to background checks.” And by a smaller but still healthy 64% to 36% they favored “banning high-capacity ammunition magazines that hold more than 10 rounds.”

The gunman in Uvalde appears to have carried seven 30-round magazines, authorities in Texas have said.

So why, in the face of such large majorities, does Congress repeatedly do nothing?

One powerful factor is the belief among many Americans that nothing lawmakers do will help the problem.

Asked in that same Pew survey whether mass shootings would decline if guns were harder to obtain, about half of Americans said they would go down, but 42% said it would make no difference. Other surveys have found much the same feeling among a large swath of Americans.

The argument about futility is one that opponents of change quickly turn to after a catastrophe. It’s a powerful rhetorical weapon against action.

“It wouldn’t prevent these shootings,” Sen. Marco Rubio (R-Fla.) said on CNN on Wednesday when asked about banning the sort of semiautomatic weapons used by the killer in Uvalde and by a gunman who killed 10 at a Buffalo, N.Y., supermarket 10 days earlier. “The truth of the matter is these people are going to commit these horrifying crimes — whether they have to use another weapon to do it, they’re going to figure out a way to do it.”

Republican Texas Gov. Greg Abbott made a similar claim at his news conference on Wednesday: “People who think that, ‘well, maybe we can just implement tougher gun laws, it’s gonna solve it’ — Chicago and L.A. and New York disprove that thesis.”

The facts powerfully suggest that’s not true.

Go back 15 years: In 2005, California had almost the same rate of deaths from guns as Florida or Texas. California had 9.5 firearms deaths per 100,000 people that year, Florida had 10 and Texas 11, according to data from the National Center for Health Statistics.

Since then, California repeatedly has tightened its gun laws, while Florida and Texas have moved in the opposite direction.

California’s rate of gun deaths has declined by 10% since 2005, even as the national rate has climbed in recent years. And Texas and Florida? Their rates of gun deaths have climbed 28% and 37% respectively. California now has one of the 10 lowest rates of gun deaths in the nation. Texas and Florida are headed in the wrong direction.

Obviously, factors beyond a state’s laws can affect the rate of firearms deaths. The national health statistics take into account differences in the age distribution of state populations, but they don’t control for every factor that might affect gun deaths.

Equally clearly, no law stops all shootings.

California’s strict laws didn’t stop the shooting at a Taiwanese church in Laguna Woods this month, and there’s no question that Chicago suffers from a large number of gun-related homicides despite strict gun control laws in Illinois. A large percentage of the guns used in those crimes come across the border from neighboring states with loose gun laws, research has shown.

The overall pattern is clear, and it reinforces the lesson from other countries, including Canada, Britain and Australia, which have tightened gun laws after horrific mass shootings: The states with America’s lowest rates of gun-related deaths all have strict gun laws; in states that allow easy availability of guns, more people die from them.

Fear of futility isn’t the only barrier to passage of national gun legislation.

Hard-core opponents of gun regulation have become more entrenched in their positions over the last decade.

Mostly conservative and Republican and especially prevalent in rural parts of the U.S., staunch opponents of any new legislation restricting firearms generally don’t see gun violence as a major problem but do see the weapons as a major part of their identity. In the Pew survey last year, just 18% of Republicans rated gun violence as one of the top problems facing the country, compared with 73% of Democrats. Other surveys have found much the same.

Strong opponents of gun control turn out in large numbers in Republican primaries, and they make any vote in favor of new restrictions politically toxic for Republican officeholders. In American politics today, where most congressional districts are gerrymandered to be safe for one party and only a few states swing back and forth politically, primaries matter far more to most lawmakers than do general elections.

Even in general elections, gun issues aren’t the top priority for most voters. Background checks and similar measures have wide support, but not necessarily urgent support.

Finally, in an era defined by “negative partisanship” — suspicion and fear of the other side — it’s easy to convince voters that a modest gun control proposal is just an opening wedge designed to lead to something more dramatic.

That leads to a common pattern when gun measures appear on ballots: They do less well than polling would suggest.

The same thing happens to measures in Congress. Nine years ago, for example, supporters of gun control made their last big push for legislation, after the slayings of 26 people, including 20 children, at Sandy Hook Elementary School in Newtown, Conn.

Then, as now, polls showed strong support for requiring background checks for sales that currently evade them. But support for the legislation was sharply lower than support for the general idea, Pew found.

Almost 8 in 10 Republican gun owners favored background checks in general, they found, but when asked about the specific bill, only slightly more than 4 in 10 wanted it to pass. When asked why they backed the general idea but opposed the specific one, most of those polled cited concerns that the bill would set up a “slippery slope” to more regulation or contained provisions that would go further than advertised.

Faced with that sort of skepticism from voters, Republican senators who had flirted with supporting the bill mostly walked away, and it failed.

Then-Vice President Joe Biden led the unsuccessful effort to pass that bill. Nearly a decade later, the political factors impeding action have only grown more powerful.