Lee Jun-seok, a 36-year-old politician with no experience as a lawmaker, swept to victory Friday in the primary for the upcoming election to pick the new chairman of the main opposition party.

Lee was among the final five candidates selected through opinion polls to compete in the People Power Party's (PPP) chairman election on June 11, according to the party's election management committee.

The former member of the party's supreme council was followed by former four-term lawmaker Na Kyung-won and incumbent five-term Rep. Joo Ho-young -- both of whom served as floor leaders -- as well as two other high-profile incumbent lawmakers.

The primary narrowed down the eight-horse chairman race to five candidates through opinion polls evenly divided between party members and private citizens. The party committee did not officially release the rankings of the polls, but party sources said Lee garnered a lion's share of support at 41 percent. Na and Joo had 29 percent and 15 percent, respectively, they said.

A Harvard graduate, Lee joined the biggest conservative party in 2011 as a member of an interim emergency leadership council at the age of 26 and went on to become a reform icon.

With no record of serving a parliamentary term, Lee entered the PPP's leadership race as an underdog. But his surprise opinion poll advance prior to the primary, mainly backed by young voters, has been widely seen as reflecting voters' calls for reforming the unpopular image of the conservative party.

The PPP is slated to pick its new chairman in a party convention on June 11 through opinion polls to consist of voting by party members for 70 percent and voting by private citizens for the remaining 30 percent.

The rival ruling Democratic Party (DP) was put on edge by the unexpected ascent of the young politician, which could possibly portend a major shift in public opinion ahead of next year's presidential election in March.

"This scene shows how supporters of the opposition party long for a change of power (in the presidential election)," an incumbent DP lawmaker said on condition of anonymity. (Yonhap)