SEOUL, South Korea — A close political ally of President Moon Jae-in of South Korea conspired with a team of online bloggers to illegally influence public opinion ahead of Mr. Moon’s election last year, a special counsel said Monday.
The special counsel, Huh Ik-bum, whose investigation was authorized by the National Assembly, found no evidence that Mr. Moon himself was involved in the alleged scheme. Mr. Huh also did not determine whether or how much Mr. Moon profited politically from the online operation.
But the alleged involvement of Kim Kyoung-soo, one of Mr. Moon’s closest aides, is a political setback for Mr. Moon, who has vowed to set himself apart from South Korea’s former presidents and their ethical scandals. Almost all of South Korea’s presidents, including Mr. Moon’s immediate predecessor, Park Geun-hye, were entangled in corruption scandals that implicated them or their aides and relatives.
Mr. Kim was accused of working with an internet blogger named Kim Dong-won, known widely here by his blogging alias “Druking.”
Druking and his team of bloggers, in collaboration with Mr. Kim, posted numerous online comments or generated millions of “likes” or “dislikes” to enhance perceptions of Mr. Moon in the six months leading up to his May election last year, the special counsel said. Their operation continued until early this year, using special computer software to produce more than 99 million “likes” or “dislikes,” he said.
Mr. Kim, Druking and several others were indicted over the weekend on election-law violations and other criminal charges, the special counsel said. Mr. Kim was accused of promising an acquaintance of Druking a government job in return for his work, he said.
Mr. Kim, then a lawmaker affiliated with Mr. Moon’s Democratic Party, served as a key adviser for Mr. Moon when Mr. Moon campaigned for the snap presidential election that was called after Ms. Park was impeached and ousted on charges of bribery and abuse of power.
Mr. Kim has denied involvement in Druking’s online operations and said he would prove his innocence at court. Despite the scandal and the headlines it generated, Mr. Kim was elected governor of South Gyeongsang Province in southeastern South Korea in June.
Mr. Moon’s office has also denied that the president was involved. There was no immediate comment from the office on Monday.
The so-called Druking-gate scandal began in January, when Mr. Moon’s party asked the police to investigate what it called “fake news” undermining the party. The party at the time suspected that some bloggers were illegally using software to increase the number of “likes” on online comments attacking Mr. Moon, including his decision to form a joint South-North Korean women’s ice hockey team for the Winter Olympics in February.
But suspicion soon turned to Druking and his team, who were now attacking Mr. Moon and his government after Mr. Kim failed to keep his promise to provide Duking’s acquaintance with a government job, according to investigators.
As the scandal spread, the rival political parties later agreed to the appointment of a special counsel to investigate it.
The Druking investigation followed another opinion-rigging scandal, in which South Korea’s government intelligence agency was accused of running a clandestine online operation to help Ms. Park’s 2012 election.
Last August, Won Sei-hoon, former director of the National Intelligence Service, was sentenced to four years in prison on charges of ordering the online campaign.
In the lead-up to the 2012 election, Mr. Won directed a secret team of psychological warfare agents to work with hired private bloggers on an online smear campaign against Ms. Park’s political rivals, including Mr. Moon, according to the prosecutors’ indictment.