A new Quinnipiac poll out today reports that 56 percent of Americans support a ban on assault weapons (with 39 percent opposed), and the same percentage support a ban on high-capacity magazines (with 40 percent opposed). But the conventional wisdom, according to scores of reporters, and aides serving several prominent Democrats, is now that only the the ban on high-capacity magazines — not the one on assault weapons — is politically possible. Theories for this are legion: the weapons ban is actually kind of useless, or too controversial, or too late. Yet if public support is there, why is it so politically contentious? Why ban only high-capacity magazines, and not the guns themselves?

Well, first of all, that's pretty much the breakdown you see in other polls between the population of gun-rights advocates and gun-control proponents — it's always a kind of 50/50 majority, pushing just beyond the margin of error (plus or minus 2.3 percentage points in the latest one). But it's useful to look at how gun-rights advocates frame the debate over gun violence. For many of them, every measure of controlling guns poses a threat to the basic ability to own and use any kind of firearm. Hence headlines such as "Obama is coming for your guns," which was recently printed in the Washington Times. On the other hand, restrictions that don't outright ban certain guns, but instead make it harder to buy them (e.g., widely supported background checks, even if Wayne LaPierre thinks they're useless), or to use them for extended periods of time (e.g., the ban on high-capacity magazines) tend to be seen as "practical" concessions, even among members of the National Rifle Association, despite the violent warnings of their own NRA leaders. (Update: NRA President David Keene told the AP today that he's confident an assault ban won't pass.)

There's also a bit of political theater at work in Dianne Feinstein's weapons ban. It is a broad policy, one that would require the mass forfeiture of a lot of guns. This is so unpalatable to Republicans that Senate Democrats are likely using it as leverage to extract deals on limiting magazine capacities and background checks. Even White House Press Secretary Jay Carney insisted several times yesterday that President Obama wanted to see the assault-weapons ban reach a vote on the floor — three days after Obama said as much in front of a Super Bowl audience. The weapons ban, then, continues to be a "sacrificial lamb" — the one big concession gun control advocates must make to pass any kind of reform. The "sacrificial" part is only confirmed when it becomes clear that a majority of Americans — if not an overwhelming one — supports the ban. Such is the reality of a split Congress, even as a Senate bill approved by Majority Leader Harry Reid is expected soon, even as it probably won't get anywhere.