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Video "trackers" are a mainstay on the campaign trail nowadays. Dispatched by candidates to shadow their rivals, they lurk in the crowds and the receiving lines waiting for the opponent to slip up, then capture the embarrassing moment on camera and post it online.

But this season, Democrats are taking the practice to a new and, some say, uncomfortable level by recording the homes of some Republican incumbents.

Two of the recent targets this year have been Ohio Rep. Jim Renacci and Wisconsin Rep. Reid Ribble, whose homes appear in roughly 30-second video clips posted online.

“It really crosses a line,” Ribble told Fox News. “I think it’s fair game for a tracker or the other party to tape what you’re saying. But this doesn’t do anything for them or the political process. And quite frankly it really disturbed my wife.”

In the Ribble video, posted online June 18, his Wisconsin home is filmed from several different angles on a windy day. It's unclear whether anyone was home when the video, which has no sound, was shot. The Renacci video follows the same formula -- straight, raw footage of the congressman's home posted to YouTube.

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Democrats are defending the practice. They say the videos of GOP members' homes -- which are generally spacious, nice-looking dwellings -- expose the fact that congressional Republicans used this session to help the wealthy and themselves.

“House Republicans have spent this entire Congress trying to hide that they’re protecting benefits for millionaires and perks for themselves instead of protecting the middle class. But we won’t let them keep it secret any longer,” said Jesse Ferguson, spokesman for the Democratic Congressional Campaign Committee.

The rival National Republican Congressional Committee also uses trackers, but in a more limited scope, spokesman Paul Lindsay said.

“Our trackers serve as eyes and ears to hold Democrats accountable in public events and public spaces only,” he said. “Anything beyond that would be a violation of our policy.”

Ribble acknowledges being a successful businessman, but said he and his family live in a middle-class home in a middle-class neighborhood.

Renacci, meanwhile, is in a close race with another incumbent, Democrat Betty Sutton, in the state’s redrawn 16th Congressional District. He suggested Sutton has had few accomplishments during her tenure in Congress, leaving her to instead attack him.

“It’s amazing they would stoop this low,” Renacci said.

The Sutton campaign, though, said the tracker was not one of their employees.

"I would hope that all political trackers respect the personal privacy of the Renacci family and the families of all candidates so that the differences between the candidates on real issues Ohio voters care about can be presented," Sutton said in a statement. "Voters deserve to hear about my work focused on fighting for jobs, protecting Medicare, and creating opportunities for the middle class in Ohio and Congressman Renacci's record of supporting tax breaks for companies that outsource jobs and voting to end Medicare as we know it, and we will continue to work in a respectful way to expose Renacci's harmful record."

Two other Republicans reportedly were the target of aggressive tracking -- Rep. Mike Coffman, of Colorado, and David Valadao, a Republican in the California state Assembly. The Coffman video was posted by a group called Colorado Fair Share, though a representative with the organization could not be reached for comment. That clip shows footage of Coffman's upscale neighborhood, and briefly shows a woman asking an apparent neighbor about Coffman's whereabouts when he doesn't answer the door.