If you're thinking that last week's tragedy in Newtown, Conn., makes it likely that Congress will soon pass stricter federal gun laws, remember this: People thought the same thing in 2011, after a gunman shot into a Tucson crowd, killing six and injuring others, including Gabrielle Giffords, one of the House of Representatives' own members.

Support for gun control swells after a mass shooting. But then, just as quickly, it tends to ebb, and opponents are happy to wait the process out.

Tougher gun-control laws face an array of obstacles. The National Rifle Association and its allies are still a powerful lobby. The fervor for more regulation is almost exclusively among Democrats; the Republican majority in the House is still solidly opposed. And there's that inevitable erosion of public attention once the heartbreaking images of funerals fade.

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But it's possible that the latest round of calls for regulation could end differently, and not only because the murder of 20 young children is so horrifying.

This time, the debate will take place in a very different political landscape, and that's probably more important, in Congress' calculations, than the emotional impact of the Newtown murders.

Consider the differences between today and last summer, when there was a brief clamor for stricter gun laws after a gunman killed 12 people in an Aurora, Colo., theater. Back then, it wasn't clear whether President Barack Obama could win a second term, and it seemed likely that the GOP would retake the Senate. Congressional Republicans saw no reason to compromise, and Obama didn't have political capital to waste.

When the president was forced to talk about the issue in an October debate, he began this way: "I believe in the 2nd Amendment. We've got a long tradition of hunting and sportsmen and people who want to make sure they can protect themselves."

But on Wednesday, when he announced that he was directing Vice President Joe Biden to bring him proposals for quick action against gun violence, Obama's tone was different. For the first time, he made gun control a formal part of his second-term agenda. "I will use all the powers of this office to help advance efforts aimed at preventing more tragedies like this," he said. "We won't prevent them all, but that can't be an excuse not to try."

On Election Day, when Obama won handily, it wasn't votes from gun owners that put him over the top. Instead, the president won by mobilizing a Democratic majority among groups that are overwhelmingly in favor of gun control: women, suburban voters and Latinos.

The most important number in this week's polls on gun control isn't the spike in support for more regulations - 54 percent in a Washington Post/ABC News poll this week, the highest in five years; that was to be expected. More important is the demographic breakdown of that support. Democrats, college-educated voters, women and minorities favor stricter gun regulations by significant majorities. Opposition to gun control is concentrated among white men, especially white men who didn't go to college.

Those demographics have several political consequences.

First, the opponents of gun control are mostly voters Obama and his party have already lost to the Republicans, so by being cautious on the issue, Democrats aren't gaining much.

Second, if Obama wants to solidify his coalition, he probably needs to respond to its members' desire for tougher gun control. For the president, that's not a hard sell. As a senator, he supported the now-defunct ban on assault weapons. When he spoke in Newtown, his passion appeared genuine. And with no more elections to face, he's free to pursue the agenda he wants.

Third, to some Democrats, the gun issue is an opportunity to try to make Republicans look like a party dominated by rural white males, an endangered species.

An important sign of the shift among Democrats were statements from senators who have opposed new gun-control measures in the past but are rethinking their position. They include Senate Majority Leader Harry Reid of Nevada, Joe Manchin III of West Virginia and Mark R. Warner of Virginia.

Already, a rough strategy is taking shape among Democrats in the Senate: Propose narrow, limited gun control measures such as improved background checks on gun buyers and bans on oversized ammunition magazines (like those used by the Newtown shooter), and then dare Republicans to oppose them. Those ideas appear to have broad support, even among many gun owners.

But that narrow approach may be pre-empted by Obama, who asked Biden to draw up options for next year that could include broad legislation as well as lesser changes that can be made by executive order. The president said he supports not only bans on assault weapons and high-capacity magazines but also tougher regulation of firearms sales at gun shows.

Did the tragedy in Newtown produce a sea change in the politics of gun control? That remains to be seen; there's no sign that Republican opposition has wavered. But it did produce an unsought opportunity for gun control advocates - if they can keep public pressure high and expectations low.

Doyle McManus is a columnist for The Los Angeles Times. Readers can email him at doyle.mcmanus@latimes.com.

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