"Are the president's kids more important than yours?" the deep and dramatic-sounding voice intoned. "Then why is he skeptical about putting armed security in our schools when his kids are protected by armed guards at their school?"

When the National Rifle Association aired its 35-second TV spot last month, suggesting that President Barack Obama has a double standard on school security and seemingly using his daughters as props, the White House quickly labeled it "repugnant and cowardly." But the commercial was another in a long line of bare-knuckled NRA advertisements, many of them controversial but also compelling attacks that have come to define the organization.

Decade after decade, these provocative broadsides have been the product of one of the longest collaborations in the history of advertising, and they have all originated from the same advertising and public relations agency, Oklahoma City-based Ackerman McQueen, and its Alexandria, Virginia, subsidiary, the Mercury Group.