Ban Ki-moon returns to South Korea in bid to lead it

Former U.N. chief faces an increasingly rocky political landscape after presidential impeachment

Ban Ki-moon, a former United Nations chief and prominent international figure, returns on Thursday to his native South Korea in an increasingly uphill effort to succeed the nation’s recently impeached president.

After leading the polls for months, Mr. Ban’s support has recently eroded due to perceptions his policies would be aligned with President Park Geun-hye’s graft-tainted administration and his support of an unpopular deal with Japan to settle a World War II-era rift.

The New York indictment of Mr. Ban’s brother and nephew in a foreign-bribery case on Tuesday risks further harming his candidacy even though Mr. Ban