Liberal groups didn't skimp on advertising against Republicans who opposed the stimulus bill, and their attacks haven't been limited to the GOP. MoveOn.org has been quietly taking aim at Democratic congressmen who voted against the final version of the bill with an online advertising effort that places small ads next to Google searches of the lawmakers' names.

MoveOn is just finishing up the two-week Google AdWords campaign, intended to praise or censure centrist Democrats for their position on the stimulus. Depending on the target's vote, the ads send users to a page highlighting the number of jobs that will be created or to one featuring the lawmaker's contact information. A similar campaign is in the works for the current omnibus spending legislation, but MoveOn's economic campaign director, Daniel Mintz, said he doesn't have any specific plans laid out yet.

This time around, Reps. Bobby Bright of Alabama, Walt Minnick of Idaho, Collin Peterson of Minnesota and Heath Shuler of North Carolina were among MoveOn's top targets. Sens. Mary Landrieu of Louisiana and Evan Bayh of Indiana meanwhile earned positive ads for their "yea" votes.

While MoveOn has advertised online for years now, this is the first time the group has launched a search engine campaign "specifically calling out legislators of any kind," Mintz said. Indeed, the progressive group is catching on to a developing trend: turning lawmakers' names into online lobbying tools.

The ads were primarily running in the lawmakers' districts, meaning they will likely not appear alongside searches conducted on the Hill -- or anywhere else outside the target area. This "geo-targeting," plus the fact that the ads don't necessarily appear for every search, makes it difficult to confirm the extent of the ad buy.

When asked about any possible backlash from Democrats, who usually enjoy MoveOn's support, Mintz said he wasn't aware of any. "We're not the party, so that gives us the flexibility when Democrats are voting against their constituents, we can call them out for it," Mintz said.

A request for a comment from the Democratic Congressional Campaign Committee was not returned.