"When I see those maps, it does leave me with a bit of a sick feeling in my stomach"

With tools like eightmaps — and there are bound to be more of them — strident political partisans can challenge their opponents directly, one voter at a time. The results, some activists fear, could discourage people from participating in the political process altogether.

That is why the soundtrack to eightmaps.com is a loud gnashing of teeth among civil libertarians, privacy advocates and people supporting open government. The site pits their cherished values against each other: political transparency and untarnished democracy versus privacy and freedom of speech.

“When I see those maps, it does leave me with a bit of a sick feeling in my stomach,” said Kim Alexander, president of the California Voter Foundation, which has advocated for open democracy. “This is not really the intention of voter disclosure laws. But that’s the thing about technology. You don’t really know where it is going to take you.”