"According to The New York Times, Democratic organizations like American Bridge 21st Century employ full-time workers to carry high-tech video cameras to GOP events where candidates interact with voters. They also staff a headquarters where a video archive is compiled, ready to be used at the right moment during the campaign season.
"The goal is to use candidates' own mistakes against them, dealing a knockout blow in the process."
Media Matters and Dem Groups Form Organization to Track GOP Candidates with Army of Videographers "Republicans also have trackers, but so far have not assembled the kind of centralized video archive of political caught-on-tape moments that their rivals envision. “Our obligation here is to get these guys on the record with what they really believe so they can’t walk away from their record,” said Rodell Mollineau, a former aide to Senator Harry Reid of Nevada and the group’s president. "
New Haven Independent ...“With trackers, it’s hard to maintain privacy or ability to have off-the-record conversations, and that, I think, is damaging,” noted blogger Aldon Hynes. “It’s especially damaging in that it promotes ‘gotcha’ journalism that misses the context of the story.”
....
"Occhiogrosso’s campaign had a guy with a video camera following Lamont around, too. Asked if he was tracking Lamont, the camera man (at right in photo) replied, “I don’t know what you’re talking about.”"
As this article states, Democrats also spy on Democrats.