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Gun control advocates have urged bans on assault weapons and high-capacity magazines after all of the mass killings over the last four years, but watched as Republicans and Democrats, including President Obama, ignored the issue.

But that could change after the deadly shooting at Sandy Hook Elementary in Newtown, Connecticut. Here’s why:

1. This shooting is different

It’s unfortunate but also unmistakably important that 20 very young schoolchildren were the victims. The shooting has gripped and angered the public and lawmakers in a powerful way, and that will influence politicians in both parties. The residents of Newtown could emerge as a powerful voice in politics and make it harder for groups like the National Rifle Association to defend allowing the possession of the weaponry used in the shooting.

2. President Obama will lead on the issue

Democratic strategists, including those advising the president, have long been wary of this issue, believing voters in the South and Midwest will turn against the party if it pushes gun restrictions. After the Tucson shooting in 2011 and the one in Colorado earlier this year, Obama’s aides quickly downplayed taking any action on gun control.

But Obama no longer has to worry about winning reelection. His comments on Friday and Sunday suggested he is more determined than before to push for legislation that would put new gun limits in place, and his aides told the Wall Street Journal Sunday that he would push for limits on high-capacity magazines. Leading Democrats in the Senate, such as New York’s Chuck Schumer, say they will introduce legislation.  If Obama strongly calls for gun control, he will have allies throughout his party.

Just as importantly, Democrats will push Obama on the issue. No longer worried about making sure Obama wins reelection, party officials can more easily demand Obama and his team take action. So can the supporters who backed him in 2008 and 2012. It’s easy to see Obama shifting to a bolder stance on gun control, as he has on gay marriage. And a strong push by Obama would like to force some kind of compromise by Republicans on the issue, even if a comprehensive gun control bill is not passed.

To be sure, there is one big challenge: a bloc of Democrats from more conservative states, such as Arkansas’ Mark Pryor, are up for reelection in 2014 and may be wary of backing gun control and then having the NRA campaign against them in 2014.

3. The voices of gun-control advocates are stronger than ever

More than in past shootings, voices beyond traditional gun control backers emerging to call for action. One of the most surprising was Fox’s Rupert Murdoch, who declared on Twitter “We have to do something about gun controls.”

Ultimately, a bloc of Republicans will have to buck a core tenet of the modern GOP: strong, unquestioned opposition to gun control laws. But this is the biggest chance for greater gun control measures to pass in a decade.

Follow Perry Bacon Jr. on Twitter at @perrybaconjr