Video trackers - hired by political groups or the party to record the movements and statements of their opponents - are hardly anathema to Brown. He benefits from one, too. A tracker for the Massachusetts Republican Party follows Warren to all her events. This campaign season, the field is more crowded than ever. Along with state political parties, National interest groups have hired trackers, dispatching them to the hottest congressional races around the country. And no race is more closely watched than the Brown/Warren contest.