WASHINGTON -- Sad yet riveting, like a wreck by the side of the road, Cindy Sheehan, a plaything of her own sincerities and other peoples' opportunisms, has already been largely erased from the national memory by new waves of media fickleness in the service of the public's summer ennui. But before she becomes fully relegated to the role of opening act for more durable luminaries at anti-war rallies, prudent Democrats -- those political snail darters, the emblematic endangered species of American politics -- should consider the possibility that, although she was a burr under the president's saddle for several weeks,...