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 doesn’t appear to be 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 marginalize Republicans and make them look like a party dominated by rural white males, an endangered species in the long run.

An important sign of the shift among Democrats were statements from several senators who have opposed new gun control measures in the past but are now rethinking their position. They include Senate Majority Leader Harry Reid of Nevada, Joe Manchin III of West Virginia and Mark R. Warner of Virginia, a potential 2016 presidential candidate.

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.