A Bachmann spokesman told the Minneapolis Star-Tribune:
We're out. It comes down to conflicting advice as to how these profits are going to be used after the fact. We'd rather err on the side of caution than do it and find out it's improper... with somebody saying 'they're using the money from an event you were at to support this and this,' which comes as a direct conflict with what you're doing as a member of Congress.
Bachmann's office had earlier said it was concerned about the possibility of violating Congressional ethics rules.
Sarah Palin is currently still scheduled to speak, but is reported to be under pressure to bow out as well.