As Radley Balko noted this morning, a new CNN poll finds no shift in public opinion regarding gun control following the recent mass shooting in Tucson. The lack of change is similar to what was seen in the wake of other high-profile gun crimes, and it makes sense. If you do not think gun control is a good way to prevent violence—if you believe that it mainly serves to disarm potential victims, rather than deter armed lunatics or run-of-the-mill criminals—dramatic evidence that firearms can be used for evil purposes is not likely to change your mind. Furthermore, the specific policy proposals covered by these polls generally have little or nothing to do with the event that put gun control in the news.
The CNN survey (PDF), for instance, asked respondents whether they support "a ban on the manufacture, sale and possession of semi-automatic assault guns, such as the AK-47." Neither assault gun nor the more commonly used term assault weapon has any fixed meaning; it is whatever legislators say it is, and typically they focus on scary, militaristic appearances, as opposed to features that make a practical difference in the hands of criminals. It's not clear what people have in mind when they tell pollsters (as 61 percent of the respondents in this poll did) that they support a ban on "assault weapons," a term that was adopted by the gun control lobby to foster confusion between fully automatic military firearms (assault rifles) and semi-automatic civilian models. But it's a fair bet that many of them are thinking of machine guns. Note that CNN cited the AK-47, an assault rifle that can fire continuously as well as one round at a time, as an example of a "semi-automatic assault gun."
In any case, the gun used to kill six people in Tucson, a Glock 19 pistol, is a popular self-defense choice that has never been classified as an "assault weapon." Seung-Hui Cho used the same handgun, along with a Walther P22, in the 2007 Virginia Tech shooting rampage, which killed 32 people. Likewise, George Joe Hennard used two ordinary handguns, a Glock 17 and a Ruger P89, in his 1991 attack on a Luby's restaurant in Killeen, Texas, which killed 23 people. Although neither of those guns was covered by the federal "assault weapon" ban, Sarah Brady still cited the Killeen massacre as a reason for Congress to approve the law.
Another specific proposal mentioned in the CNN survey—a ban on magazines holding more than 10 rounds—does at least have some connection to the Tucson massacre, since Jared Lee Loughner reportedly used such magazines in his attack. According to the New York Times account, Loughner emptied one 30-round magazine, loaded a second one that jammed, and was trying to load a third when he was tackled and disarmed. Rep. Carolyn McCarthy (D-N.Y.), who plans to introduce legislation next week that would limit magazines to 10 rounds, argues that Loughner might have killed and injured fewer people if he had to reload sooner. She made a similar argument after Colin Ferguson used a Ruger P89 with 15-round magazines in his 1993 attack on the Long Island Rail Road, which killed six people, including her husband (an incident that motivated her to run for office).
McCarthy's counterfactual may be correct. But it's important to note that her legislation, like a similar provision that was included in the now-expired federal "assault weapon" ban, would have no impact on magazines already in circulation. Hence a determined mass murderer could still obtain 30-round magazines. Alternatively, he might compensate for smaller magazines by bringing multiple weapons or by taping magazines together to facilitate reloading. And if it's true, as commenters here have argued, that 30-round magazines are especially prone to the sort of misloading that Loughner experienced right before he was tackled, the upshot of smaller magazines would not necessarily have been fewer casualties. For what it's worth, magazine size does not seem to have made any difference in the Virginia Tech and Killeen attacks, both of which killed far more people than died in Tucson.
The possibility that legislation like McCarthy's could make a difference in rare events like the Tucson massacre has to be weighed against the legitimate interests of gun owners who prefer large-capacity magazines for range shooting or envision self-defense scenarios in which the extra rounds would be useful. (Having lived in L.A. during the 1992 riots, I don't consider those scenarios wildly far-fetched.) As is generally the case with gun control, the cost is borne mainly by law-abiding citizens, while the public safety payoff is dubious at best.
Robert Farago discusses high-capacity magazines at The Truth About Guns.