The shooting of nearly 30 people in a school in Connecticut has restarted the debate nationally over whether President Obama and Congress should support greater gun control measures.

Some liberals in Congress are strongly pushing Obama on an issue on which he has said and done little as president, despite urgings from figures like New York Mayor Michael Bl0omberg.

“Yet another unstable person has gotten access to firearms and committed an unspeakable crime against innocent children.  We cannot simply accept this as a routine product of modern American life.  If now is not the time to have a serious discussion about gun control and the epidemic of gun violence plaguing our society, I don’t know when is.  How many more Columbines and Newtowns must we live through?  I am challenging President Obama, the Congress, and the American public to act on our outrage and, finally, do something about this,” said Rep. Jerry Nadler, a Democrat from New York.

Rep. Nina Lowey, also a Democrat from New York said, “We cannot tolerate mass shootings as a mere inconvenience or a normal part of our everyday lives.  Easy availability of the deadliest weapons to the most dangerous people has cost countless lives and caused immeasurable suffering, never more so than today. ”

White House officials are so far not commenting on the gun control debate. At a press briefing, spokesman Jay Carney repeatedly sidestepped policy questions, saying they could be discussed later, but not today in the midst of the tragedy. But he noted the president supports an assault weapons ban. (The gun used in the shooting, a 223-caliber rifle, could be banned nationally under such a provision.)

Gun control has long been a controversial political issue. Democratic strategists have advised candidates to avoid the issue, arguing it hurts the party with rural and white male voters. Many Republicans and some Democrats are opposed to limits on guns on principle, and the National Rifle Association is a powerful, pro-gun-rights group that politicians in both parties fear.

Democrats opted against pushing through gun control measures when they controlled both houses of Congress in 2009 and 2010, declining to put the assault weapons ban back in place. Once they gained control of the House, Republicans also avoided the issue, even after then-Rep. Gabrielle Giffords, a Democrat from Arizona, was shot last year in a Tucson shooting that killed six people.

Some analysts said Democrats have long misread the politics on this issue, arguing there are plenty of voters who back gun control and would support Democrats enacting legislation like an assault weapons ban.

“Gun control is now overwhelmingly unpopular among the portions of the white electorate Obama is least likely to win anyway—and maintains solid majority support among the Americans most likely to actually vote for him,” the National Journal‘s Ron Brownstein wrote earlier this year.

Obama now does not have to worry about facing reelection himself. But it’s still unclear if he will use his bully pulpit to push gun control, as he has on immigration reform, raising taxes on the wealthy and health care reform. It’s also not clear Democrats in states with lots of white working-class voters would support such a push and face a potential backlash.

And the biggest unknown is Republicans, who control the House of Representatives and could block any gun legislation from becoming law. They have shown no sign of ending their ironclad opposition to new gun control legislation.