Former U.N. secretary-general Ban Ki-moon feeds a elderly woman at a social welfare facility in Eumseong, South Korea, January 14, 2017. [Photo/Agencies]

SEOUL - It has been an inauspicious return to crisis-plagued South Korea for former U.N. chief Ban Ki-moon, once the odds-on favorite to be the next president, who has been ensnared in a family corruption scandal and struggled with a sceptical press.

Ban, 72, has been unable to capitalise on his much-anticipated homecoming after a decade as secretary-general of the United Nations in New York. Since his return on Jan. 12, he has cut a sometimes-irritable figure in public and been pilloried for a series of perceived PR gaffes - all without announcing any intention to run for president.

Now the United States has asked South Korea to arrest his brother, Ban Ki-sang, on charges that he engaged in a bribery scheme to carry out the sale of a Vietnamese building complex.

The timing of the case could hardly be worse for Ban, whose high international profile and clean image were expected to be assets as he returned to a nation reeling from a presidential corruption scandal. President Park Geun-hye has been impeached by parliament and stripped of her powers while a court decides her fate.

Ban Ki-moon apologised on Saturday for family members who had caused public concern. "I have absolutely no knowledge of this case," he said in a statement.

However, a Realmeter poll released on Monday showed Ban's support slipping from 22.2 percent last week to 19.8 percent, compared with 29.1 percent for Moon Jae-in of the opposition Democratic Party.

The poll numbers are volatile and analysts say it is too early to count out Ban. However, if Moon holds his lead, he would become the first liberal to be elected president in nearly a decade.

Ban has yet to affiliate himself with a party but had been expected to run as a conservative.

If the impeachment vote against Park is upheld by the Constitutional Court, she will have to quit and an election would be held two months later. A ruling is expected as soon as next month.

Ban has a team of politicians and former diplomats supporting him and has made several campaign-style appearances around the country since his return, pitching him in the full glare of the media spotlight.

SLIP-UPS

On his arrival in Seoul, Ban took the airport express train instead of a limo, but didn't know how to buy a ticket. He was pictured trying to insert two 10,000 won bills into the machine at the same time for a 7,500 won ticket.

"Couldn't you have treated it as something cute from a person who'd been in New York for a long time?" he protested at a meeting with voters and reporters in the southern city of Daegu. "I really wish they wouldn't act with malice."

Two days later, Ban visited a care home where he fed porridge to an old woman. He was criticized for wearing a bib when the old woman was not - and for feeding someone lying flat on their back.

He also dressed head to toe in protective gear to try out a disinfectant spray when most of those around him wore ordinary clothes, media said. And he was criticised for picking up a bottle of Evian mineral water from a convenience store before being told by an aide he should buy a local product.

A cartoon in the left-leaning Hankyoreh newspaper managed to combine the gaffes - Ban in protective gear and bib trying to feed a hospital patient with two 10,000 won notes with a giant bottle of Evian on his back.

Until recently, Ban had been tipped to run as a member of Park's conservative Saenuri party.

But being a Saenuri candidate looks far less attractive now because of the corruption scandal and he has been seen as likely to join a new breakaway group from the conservative bloc, the Barun Party, which has been weighing several potential candidates for president.

However, a party, funds and political machinery to support Ban could come together quickly if and when he announces he will run for president.

Kookmin University political science professor Hong Sung-gul said Ban must be disappointed by his reception.

"That's what happens when there are high expectations and you don't come in with a clear and specific message," he told Reuters.

"But it is too early to write off his campaign as being in serious trouble."

Ban himself admitted on Monday to some "clumsy moments" and irritability since his return.

"I was impatient and had passion for wanting to go and meet the people as soon as I could, so there were little mistakes," he told reporters.

"I'll take it as a tough lesson learned and try to be better prepared."??