The vaunted reputation of the agency—previously an elite unit of the Treasury Department—has always been better than its track record. The Secret Service knew it, too, but this image of competence was cultivated partly as a deterrent. After September 11, 2001, things changed because edifices and agencies that symbolically projected American power were themselves possible targets, so the nation’s security systems were hardened.

Or so we thought. Now Americans learn that despite spending $1.5 billion annually to put 6,700 officers and agents in the field, a bungling Secret Service—now housed uncomfortably inside the sprawling U.S. Department of Homeland Security—has actually put this country at risk. How did this happen?

Let’s start with the image-making. Hollywood films have traditionally portrayed the president’s protective detail as brave, resourceful, and dedicated agents confronting a confounding trio of obstacles: amazingly skilled bad guys, the reluctant cooperation of the first family, and the hidebound brass of their own agency. Except for the first conceit—would-be assassins tend to be unstable bunglers—this portrayal accurately reflects both the public’s perception and reality of life in the Secret Service, an agency that only gets noticed for its mistakes.