petition for Scott Walker as governor took place the GQP phoned my elderly Mom, failed to identify themselves, and accused her of fraudulently signing the petition and threatening that she would be in trouble. A few days later that was followed up by a knock on her door and a man saying he was "verifying" signatures and identities for the petition and he asked for her ID and a signature example. My Mom was an old school original Roosevelt Democrat and the door slammed in his face.
This sort of thing is an old tactic of intimidation that was used during labor organizing, civil rights organizing and anti-Vietnam/anti-nuke organizing activities. What they would do is be standing in the parking lot taking pictures of people, cars, license plates, very visibly making a display of writing things down all for the immediate effect of intimidation and then later they would sometimes go further based on the information they had gathered.
Awhile before all of that I was involved with an environmental activism matter and a local guy who had become a State Senator came up to me at a meeting when I was in the audience and out of the clear blue asked how my daughter liked living in her neighborhood. He specifically mentioned the neighborhood despite me never having mentioned to anybody that I even had a daughter. Not only that but she was married and had taken her husbands name so even casual connection by name wouldn't have been possible. That's when I knew that people had done surveillance investigation of the members of that small environmental group fighting for environmental justice and disclosure.