More elaborate data-mining techniques, such as logistic regression analysis, suggest that gun ownership is a more powerful predictor of whether a voter is Republican than her gender, whether or not she identifies as gay or lesbian, whether she is Hispanic, or whether she lives in the South, along with many other demographic characteristics.

And based on demographic inertia, the differences seem likely to grow over time. About 35 percent of Democratic voters aged 65 and older reported having a gun in their home, against about 25 percent of those aged 18 to 29. But gun ownership rates bore little relationship to age among Republican voters, and were constant at about 55 percent among all age groups. That might suggest that gun ownership will continue to decline among Democrats while holding steady among Republicans, further increasing the partisan gap.

Perhaps last weekend’s mass shooting in Newtown, Conn., will serve to partly reverse the partisan split in attitudes toward guns; early polls on Newtown find relatively modest differences between Democrats and Republicans on what they see as the causes of the shooting.