Max Morley stepped away from the race after acknowledging the authenticity of a door camera video showing him removing a campaign flyer for a rival candidate from a mailbox.
Morley apologized on social media, saying he "exhibited a lack of judgment."
The mailer promoted incumbent Rep. Daniel Grossberg, who has long been under pressure within his own party to resign over alleged inappropriate and coercive behavior toward women.
Grossberg remains in the race, as do two other Democrats — Cassie Lyle and Mitra Subedi.