Marlene Ross, who has been a Palm Beach County commissioner for five years, said she felt threatened by David Katz, a former county commissioner and now a lobbyist, The Palm Beach Post reported. She said she feared Katz would release pictures she had sent her boyfriend after he mentioned them at a meeting this month.
The state's attorney's office closed the case last week, officials said.
"None of the scenarios described by Ms. Ross involved behavior that could be considered criminal extortion," Daniel Funk, a member of the public integrity unit, said.
Boynton Beach Mayor Woodrow Hay called on Ross to resign Tuesday, saying a story in the morning newspaper "scars our city."
Katz called Ross' allegations "laughable at best."
"There's nothing to blackmail her over," he said.