Former Prosecutor General Yoon Seok-youl, who was nominated last week as the main opposition People Power Party’s presidential candidate, faces the task of framing himself as a capable and inclusive leader if he is to achieve a change of power with the election four months away.

After a period of soul-searching following his resignation from the top prosecutorial post in March, Yoon declared he was entering politics in June and joined the conservative opposition party a month later.

What principally enabled him to clinch the party’s presidential ticket was his record of clashing with President Moon Jae-in and his aides over investigations into sensitive cases involving them when he served as prosecutor general.

His insistence on pushing the probes forward even under daunting political pressure earned him a reputation as a figure who could restore common sense, fairness and the rule of law, which many people believe have been damaged significantly under Moon’s presidency. As a result, a majority of opposition party members threw their support behind Yoon -- despite his role in the investigation that brought down the government of conservative President Park Geun-hye and led to her impeachment and imprisonment in 2017.

His nomination as the People Power Party candidate pits the political novice against Lee Jae-myung of the liberal ruling Democratic Party of Korea in the election slated for March 9.

In his acceptance speech at Friday’s party convention, Yoon pledged to achieve a change of government without fail and to end the “politics of division and anger, corruption and plunder.”

He cast the upcoming election as a battle between common sense and senselessness and between a rationalist and a populist -- contrasting himself with Lee, who is known for his aggressive personality and his populist streak.

A poll released Friday by Gallup Korea pointed to the increased public yearning for a change of power after the next presidential election. In the poll of 1,000 South Koreans aged 18 and above, 57 percent of the respondents wanted an opposition contender to win the vote, whereas only 33 percent hoped to see the ruling party’s candidate elected. The figures represent an increase of 5 percent and a decline of 2 percent, respectively, from Gallup Korea’s poll a month earlier.

Yoon has much work to do if he is to turn the public’s aspirations for a change of government into wider voter support. A poll conducted last month showed that voter sentiment was against Yoon and Lee alike, with only about 30 percent of voters holding a favorable view of either one.

In the final vote in the conservative opposition party’s presidential primary, Yoon received overwhelming support from party members. But runner-up Rep. Hong Joon-pyo won by a significant margin in the poll of ordinary voters outside the party.

Those results highlight the need for Yoon to step up efforts to draw more support from centrists, as well as from younger voters.

In the course of the presidential primary, he hurt his own credibility with a string of gaffes and insensitive remarks. He also gave the impression of having a relatively poor understanding of policy issues, though his lifelong career as prosecutor might have to be considered.

To win the presidential contest against Lee, who stepped down from the governorship of Gyeonggi Province last month, Yoon will have to demonstrate a firm posture and suggest concrete visions and policies so that he can widen his support base among undecided moderate voters, particularly those in their 20s and 30s.

The ruling party’s contender, Lee, will also try to move closer to the center ground.

One potential risk to the campaigns of both Yoon and Lee concerns ongoing probes by the prosecution and a separate investigative agency into cases that could implicate them. The investigations in question should be carried out in a quick and impartial manner. Otherwise, it may be necessary to appoint independent counsels to handle the cases as Yoon has suggested.