SEOUL, South Korea — South Koreans voted Tuesday for a new president, with victory widely predicted for a liberal candidate who has pledged to improve ties with North Korea, re-examine a contentious U.S. missile defense shield and push sweeping economic changes.

Conservatives worry that a victory by Moon Jae-in might benefit North Korea and put South Korea at odds with its most important ally, the United States.

But Moon has been the clear favorite as the country’s powerful conservative forces struggle to regroup after a huge corruption scandal that led to President Park Geun-hye’s removal from office and arrest in March.

“This is the last challenge of my life. I’ve really done my best so far. I’ve made enormous preparations. I’m confident. I’ll strain every nerve to the last minute to be a president for all the people,” Moon, 64, said on the eve of the election.

The final opinion surveys released last week showed Moon, the Democratic Party candidate, had about a 20 percentage point lead over his two main rivals – a centrist and a conservative.

His victory would end a near decade of conservative rule by Park and her predecessor, Lee Myung-bak.

When the liberals were last in charge in Seoul, Moon served as chief of staff for then President Roh Moo-hyun. They sought closer ties with North Korea by setting up large-scale aid shipments to the North and by working on now-stalled joint economic projects.

The winning candidate will be officially sworn in as South Korea’s new president after the National Election Commission ends the vote count and confirms the winner Wednesday. The new leader will serve out a full, single five-year term.