By John Stoehr USA Today runs a daily poll on its frontpage. On Friday, the public survey results were on gun laws. “If it were harder to obtain guns legally, Americans think there would be ____ mass shootings.” Sixty-six percent said there would be far fewer or somewhat fewer mass shootings. Nearly 30 percent said no difference. (A smattering of cranks, 5 percent, said there would be more or somewhat more.) I bring this to your attention not so much to bolster the prospect of tighter gun laws (though it does), but to point out a pretty common demographic pattern – that a radical third stands …