"There's a group of people hanging out near the ballot dropbox filming and photographing my wife and I as we approached the dropbox and accusing us of being a mule," said the report, which was written by a voter in the Phoenix suburbs and obtained by The Washington Post. "They took … photographs of our license plate and of us and then followed us out the parking lot in one of their cars continuing to film."

For months in this vast desert swing state, elections officials and democracy advocates have worried that bands of activist observers hunting for fraud will harass and intimidate voters. Citizen watchdogs, organized and freelance, have advertised stakeout events to monitor the goings-ons in parking lots and other drop box locations as voters deposit their early ballots ahead of Election Day.

Monday's report, which emanated from a drop box in Mesa, just off a major roadway, was the first solid evidence that those fears might come true.