Duffy, who's appeared in Sex & the City and Law & Order, admits she was confused when a politically active worker in her New York apartment building knocked on her door to campaign for Leslie Crocker Synder.
She claims she was taken in a limo to City Hall and put infront of a camera, without understanding what was going on.
When Duffy realised she had inadvertently campaigned for Synder, she contacted the Screen Actors Guild (SAG) to investigate claims her union rights had been violated.
She explains to the New York Post, "I felt I was misled. It was totally confusing to me. She might be a very good candidate. I don't know anything about her... Usually, you sign a release when you work on a commercial. I signed nothing."
However, a campaign spokesperson has brushed off the incident as a misunderstanding, insisting organisers were under the impression Duffy had "volunteered to participate" and would not be featured in the TV spot.
The spokesperson adds: "It has since been brought to our attention that Ms. Duffy is a SAG member and wishes to be compensated for her services, and the campaign will be paying her."