WASHINGTON — The horrific Connecticut shootings are likely to change the tone of Congress’ debate over gun control and other efforts to curb violence.

But don’t look for big changes in those laws.

The Friday massacre of 26 people, including 20 children, at Sandy Hook Elementary School has shaken lawmakers like few events in recent years. Its emotional impact is comparable in recent years only to the attempted 2011 assassination of Rep. Gabrielle Giffords, D-Ariz., but this incident has been even more jarring to members of Congress and the political world.

History shows that shocks like this often result in incremental changes to gun-control laws but little more, as fierce lobbying and political concerns become paramount.

The failures to achieve major changes are mired in the kind of politics that has stifled action on controversial gun-control measures for years. The nation remains divided over how or whether to regulate firearms, and the gun lobby remains one of the Capitol’s most powerful.

The National Rifle Association alone spent more than 10 times as much as gun-control groups on lobbying last year and in the first nine months of this year, according to data compiled by the nonpartisan Center for Responsive Politics.

The center found that last year was the most active election cycle in a dozen years for gun interest groups, as they gave $3 million to candidates, 96 percent of them Republicans, through mid-October. Gun-control groups barely registered, giving only $4,000, all to Democrats.

The gun lobby was unrelenting Monday. Eric Pratt, spokesman for Gun Owners of America, said if there’s to be a discussion on gun legislation it “should lead to a greater ability to protect one’s self. . . . Sadly, they (gun-control advocates) will try to exploit this to make people less safe.”

Some Republicans agreed. Said Rep. Louie Gohmert, R-Texas: “I wish to God [the Sandy Hook principal] had had an M-4 (rifle) in her office,” so she could have taken it out and “takes his head off before he can kill those precious kids.”

Democrats countered with quick calls for gun-control action.

“We should stop making emotional room in our hearts for each year’s new round of public shootings and killing sprees,” said Rep. Raul Grijalva, D-Ariz.

Monday, though, two developments gave gun-control advocates new hope. Many Democrats, including President Barack Obama, who for years have been reluctant to speak out for tougher gun laws, aren’t holding back.

“I actually think things could change. The terrible nature of this shooting has the potential to transform the national debate,” said Darrell West, vice president and director of governance studies at Washington’s Brookings Institution.

There were some signs Monday that was occurring. “This has changed the dialogue, and it should move beyond the dialogue. We need action,” Sen. Joe Manchin, D-W.Va., an avid hunter, said on MSNBC’s “Morning Joe.”

Getting results, though, won’t be easy.

“I think that between election results and court decisions that a consensus has been settled on both sides that gun control is a non-starter,” said Keith Appell, a Virginia-based Republican strategist.

Appell said the Connecticut shooting will prompt gun-control advocates to produce legislation, “but it probably will not result in anything.”