Pressure is suddenly mounting on President Barack Obama, who promised tougher gun laws in 2008, to finally take up the gun control cause after the massacre of 20 Connecticut schoolchildren.
A chorus of Senate Democrats, including Dianne Feinstein, Richard Blumenthal and Richard Durbin added their voices to that of New York Mayor Michael Bloomberg in calling Sunday for swift action on gun control, while Republicans and the National Rifle Association remained silent in the wake of the tragedy. The time for "saying that we can't talk about the policy implications of tragedies like this is over," said Rep. Chris Murphy (D-Conn.), who won a Senate seat in the November elections.
In his remarks at a vigil in Newtown Sunday evening, Mr. Obama said he would use "whatever power this office" to prevent similar tragedies from happening. "Because what choice do we have?" he said. "We can't accept events like this as routine."
Experts say the outrage over the shooting will further mobilize politicians to take action they have avoided after previous mass shootings and will strengthen the President's hand against the powerful U.S. gun lobby. "The political environment on guns may be different today than it was even a few weeks ago," said UCLA law professor Adam Winkler, an expert on gun control.
"People are angrier than ever before after one of these shootings. The calculus in Washington may be different. President Obama is no longer worried about re-election."
Mr. Obama, who called Saturday for "meaningful action to prevent more tragedies" such as the Connecticut shooting, which also took the lives of seven adults, will have an opening to show his mettle after a top Democratic senator vowed to introduce legislation in January banning the assault weapons and high-capacity magazines used in most mass shootings.
"He's going to have a bill to lead on," Ms. Feinstein, the California senator, said Sunday on Meet the Press, promising to table her legislation on the first day of the new Congress. "We'll be prepared to go. And I hope the nation will really help."
A ban would prohibit the sale of most semi-automatic rifles that enable users to rapidly fire multiple rounds of ammunition. Seeking to head off opposition, Ms. Feinstein said her bill would exempt more than 900 types of weapons and would not apply retroactively, meaning existing owners of assault weapons could keep their guns.
Even so, the legislation would likely bring determined opposition from Republicans in the House of Representatives, though Texas congressman Louie Gohmert was the lone GOP voice willing to make the case for gun rights advocates on the Sunday political shows.
Mr. Gohmert said the principal at Sandy Hook Elementary School, who is believed to have died trying to subdue shooter Adam Lanza, would have fared better if she had been armed. He added that gun violence is lower in states that permit gun owners to carry concealed weapons.
"I wish to God [the principal] had had an M-4 in her office, locked up, so when she heard gunfire, she pulls it out and she did'n't have to lunge heroically with nothing in her hands," Mr. Gohmert said.
A 10-year federal ban on assault weapons expired in 2004, when Congress failed to renew it. Since then, state laws have increasingly favoured gun owners, while a proliferation of unregulated sales at gun shows has enabled buyers to skirt a federal regulation requiring purchasers to undergo an FBI background check.
Mr. Bloomberg, an outspoken advocate of stricter gun controls, harshly criticized Mr. Obama on Sunday for failing to fulfill his 2008 promise to renew the assault weapons bans and close the "gun show loophole." Mr. Bloomberg also complained that the background check data base is frequently out of date.
"It's time for the President to stand up and lead," the New York Mayor said on Meet the Press. "This should be his No. 1 agenda. … If he does nothing in his second term, something like 48,000 Americans will be killed with illegal guns. That is roughly the number of Americans killed in the whole Vietnam War."
Overall, there are about 33,000 U.S. gun deaths annually, including around 12,000 gun-related homicides. The number would be much higher were it not for a huge leap in the survival rates of gunshot victims due to improved trauma care in recent years.
Connecticut has among the toughest gun laws in the country, including a ban on certain types of assault weapons. The ban does not specifically cover the .223 Bushmaster semi-automatic rifle used by Friday's shooter, 20-year-old Adam Lanza. The gun is believed to have been legally registered to his mother, whom he killed before turning the weapon on students and teachers at the school in Newtown.
Experts said the challenge for lawmakers will be crafting an assault weapons ban that is broad enough to include most weapons, while preventing gun manufacturers from undermining it as they did with the previous ban.
"Part of the problem with an assault weapons ban is defining which rifles are banned or not," Prof. Winkler said. "The [previous] assault weapons ban was so poorly drafted that gun manufacturers just made some slight, superficial modifications on the firearms and sold them."
Duke University public policy professor Kristin Goss added that a new assault weapons ban faces a tough slog in Congress unless Mr. Obama takes up the charge and mobilizes public opinion in favour of it.
"I don't think any assault weapons ban can be passed without him putting it at the top of his agenda," Prof. Goss said. "And it is 99 per cent likely that any ban would have to grandfather existing weapons."
Democrats seized on public outrage over rising drug-related gun crime in the early 1990s to pass the assault weapons ban in 1994. But the bill signed by then-president Bill Clinton is seen as one of the reasons Democrats lost more than 50 House of Representatives seats in the 1994 midterm elections, as the National Rifle Association mobilized gun rights advocates.
Ms. Feinstein countered the NRA did not stop the ban from being passed and never challenged it in court on constitutional grounds.
"They knew it would be sustained from the beginning. And I believe this [new law] will be sustained as well," she said. "All of the things that society regulates, but we can't touch guns? That's wrong."