By Calvin WoodwardWASHINGTON (AP) -- The question surfaces each time a mass murder unfolds: Will this one change the political calculus in Washington against tougher gun control? The answer, after the Virginia Tech killings, the attempted assassination of Gabby Giffords, the Colorado movie-theater attack, the Wisconsin Sikh temple shootings, and more: No. But now? The massacre at Sandy Hook Elementary School in Newtown, Conn., the bloodiest attack against youngsters in the nation's history, stands as a possible tipping point after Washington's decade-long aversion even to talking about stricter gun laws. So it seems in the stunned aftermath, judging from President Barack Obama's body language as much as his statement. "We have been through this too many times," said the famously composed president, this time moved to tears. "We're going to have to come together and take meaningful action to prevent more tragedies like this, regardless of the politics." It remains to be seen whether Sandy Hook will break the usual cycle of universal shock fading into political reality. That reality is based on a combination of powerful gun lobbying and public opinion, which has shifted against tougher gun control and stayed that way. However lawmakers react this time, it's the president's call whether the issue fades again or takes its place alongside the legacy-shaping initiatives of his time, with all the peril that could mean for his party. With the murder rate less than half what it was two decades ago, and violent crime down even more in that time, gun control has declined as a political issue. But New York Mayor Michael Bloomberg, a gun control advocate, heard the familiar in Obama's initial response, despite the striking emotion. "Not enough," Bloomberg said of Obama's words. "We have heard all the rhetoric before. What we have not seen is leadership -- not from the White House and not from Congress. That must end today." The Newtown shooter brought three guns into the school, and the weapons were registered to his slain mother, according to a law enforcement official who was not authorized to discuss information with reporters and spoke on condition of anonymity. The official said a Glock and a Sig Sauer, both pistols, and a .223-caliber Bushmaster rifle were found in the school after the attack, and a fourth weapon was recovered outside.