By Sudip Kar-Gupta and Michel Rose
PARIS (Reuters) - French President Emmanuel Macron suffered a setback on Friday when one of his closest lieutenants, Benjamin Griveaux, pulled out of the race to become mayor of Paris after it was alleged he sent sexual images to a woman who is not his wife.
Griveaux, 42, is one of the "Macron boys" - the group that helped propel the former investment banker into power in 2017.
"I have decided to withdraw my candidacy from the municipal election," Griveaux said in a video statement.
He said he and his family had been subjected to months of anonymous statements defaming him, and threats to disclose private conversations stolen from him.
A new level had been reached on Thursday with "websites and social networks carrying ignoble attacks about my private life," he said.
A Russian dissident artist, Pyotr Pavlensky, published screenshots of an online chat which he said was between Griveaux and a woman who is not his wife and exposed his "hypocrisy".
The chat included a video showing a man's genitals. Griveaux has not disputed that he sent the messages.
Griveaux started in politics as an adviser to Dominique Strauss-Kahn, the former head of the International Monetary Fund whose political career ended in disgrace in 2011 over a sexual assault case on a maid in a New York hotel.
Griveaux was central to Macron's attempt to control the French capital and build a local power base for his party in mayoral elections next month.
But his campaign was already struggling, with opinion polls showing him in third place.
Macron's LREM party had chosen Griveaux to represent it in the Paris mayoral campaign over Cedric Villani, a mathematician and lawmaker.
Officials from Macron's party were expected to hold talks over the weekend to decide what to do. It was unclear whether the party would rally behind Villani, a rebel lawmaker who was expelled from the LREM last month, or field another candidate.
Asked whether he could become the Macron camp's official candidate, Villani said he was open to uniting anybody willing to support his own "progressive" agenda.
Griveaux alienated many in his own camp after his selection by referring to party rivals as "arseholes" among other insults in a leaked conversation with journalists.
Paris Mayor Anne Hidalgo as well as rival Villani both expressed support for Griveaux, saying his right to privacy should be respected.
French politicians from all camps denounced in unison the leak of private material, which many said constituted an unacceptable Americanisation of politics in France, where politicians' private lives have long been considered off limits.
"We must collectively be responsible and say: not here, not in France," LREM party head Stanislas Guerini said.
Pavlensky, who published the sex video, is best known for works of performance art including nailing his scrotum to the ground in Moscow's Red Square, and setting fire to a door at the headquarters of Russia's state security agency.
(Additional reporting by Dominique Vidalon and Elizabeth Pineau; Editing by Christian Lowe and Timothy Heritage)