The son of Virginia Democratic congressman Jim Moran has resigned from his father's campaign after an undercover video showed him discussing a plan to cast fraudulent ballots.
Patrick Moran, who had been a field director for his father's campaign, said he did not take the man seriously and humoured him, adding that he should have walked away.
His father's campaign office called the incident an error of judgment.
Project Veritas, an organisation led by activist James O'Keefe, released a video showing an undercover operative pitching a voter-fraud plan to Patrick Moran.
The plan called for casting ballots in the names of 100 voters who were registered, but rarely voted.
In the video, Patrick Moran expresses doubts about the plan but eventually tells the undercover volunteer to "look into it".