SEOUL (Reuters) - An opinion poll released on Monday in South Korea showed former U.N. Secretary General Ban Ki-moon in second place and narrowing the gap on the frontrunner among likely candidates to succeed President Park Geun-hye, who has been impeached by parliament.

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The Realmeter poll commissioned by the Maeil Business Newspaper showed former liberal opposition party leader Moon Jae-in maintaining his lead at 26.1 percent, compared with 22.2 percent for Ban.

Ban, who has made several campaign-style appearances since returning to South Korea earlier this month, has narrowed the gap, having polled 21.5 percent against Moon’s 26.8 percent a week earlier.

Ban said on Thursday that he will make a decision “soon” on his political future.

On Monday, Ban called President Park around 10 a.m. (0100 GMT) to inform her officially of his return, Ban’s spokesman Lee Do-woon said in a press release.

“I should have visited you in person. It is unfortunate that the situation is like this,” Ban was cited as saying. “I hope you will manage the situation well.”

Park was also cited in the release as congratulating Ban for his past decade working for the U.N., but did not mention her impeachment process nor the scandal at hand.

South Korea has been gripped by political crisis for months, with parliament voting overwhelmingly in December to impeach President Park over an influence-peddling scandal, a decision that must be upheld or overturned by the country’s Constitutional Court.

If the impeachment stands, an election would be held two months later. The election to a single five-year term is currently scheduled to take place on Dec. 20.

Ban, 72, planned to tour the south of the country on Monday, visiting shipbuilding docks in Geoje and a traditional market in Busan. His representatives have said Ban aims to have as much contact with the public as possible as he gears up to make a decision on his future.

On Tuesday, Ban is scheduled to visit the grave of former President Roh Moo-hyun in Bongha village, also in southeastern South Korea, before heading to Pangmok Port, near the site where a ferry sank in 2014, killing more than 300 people.

The Realmeter poll was conducted from Jan. 9 to 13 and responses were taken from more than 2,500 adults. Trailing Moon and Ban in third place was fellow Democratic Party candidate Lee Jae-myung, the mayor of Seongnam, with 11.7 percent approval, down from 12.0 percent in the previous week.

Ban’s presidential ambitions hit a hurdle last week when two of his relatives were indicted by U.S. prosecutors on Tuesday over bribery allegations. Ban has denied any knowledge of his relatives’ business affairs.

Controversy around the building deal linked to Ban’s relatives had been reported previously in South Korean media.