Spies on the trail.

In the fight for the Democratic presidential nomination, candidates are leaving nothing to chance. Behind every candidate is an army of foot soldiers whose job is to monitor and determine other candidates. These practitioners of what one political operative calls "the dark arts" work somewhat furtively, far from the flag waving, and from the candidate. They include "trackers," who monitor and record what rival candidates say at campaign stops, researchers who delve into records, and minions who e-mail these nuggets to reporters in hopes of generating negative stories. Campaigns take it as a given that they will have spies in their midst, and are fairly accommodating because they want the same courtesy in return. "It's not hostile," says Mark Kornblau, Senator John Kerry's communications director in New Hampshire. "We all know each other."