Political trends come and go in response to events. Gun control was the rage during the Clinton administration, but over the past decade or so it became an obsolete cause. After the horrific crimes in Newtown and Aurora, though, it’s staging a comeback.

One thing hasn’t changed: The agenda includes mostly measures that will have little or no effect on the problems they are supposed to address. They are Potemkin remedies — presentable faàades with empty space behind them.